First of all, if one of the mods finds this useful enough to make a sticky on it...great. If not that is fine too.
I have received quite a number of PM's lately asking about exhaust. I do not mind them, in fact I enjoy helping people out and answering their questions. If you have questions after this post, still feel free to ask them, I will answer.
I know that there are many peole on here who know more about exhausts than I do as far as the technical stuff. But, in the last two months I have done around 40 dynos with many different combinations of modifications and exhausts. The systems that I have had include the following now:
1) Full Stock set-up with 22" magnaflow muffler
2) Magnaflow Catback
3) Gibson swept side
4) Borla Dual
5) Flowmaster 40 series
6) Flowmaster 70 series
7) JBA single exit
For 2007 Titan Owners: You have the best set up from what I found with my previous 2005 model. That is a true dual in to a single out muffler. It produced the most torque of any of my systems. You can do a muffler swap with Magnaflow part number 12580 (satin stainless) or 14580 (polished stainless). This is a dual inlet/single out muffler that is wide open straight through design. I will be putting this muffler on my 07 titan in the near future after doing a baseline STOCK dyno. I need to get some miles on her first. One thing that may need to be noted. In installing this muffler, it is best to cut the drivers side pipe about 2 feet before the muffler and again at the muffler. Now take this pipe and rotate it 180*. THis is because the muffler has a center to center inlet width that is 3" less than the stock muffler.
I will provide what I observed during the whole process to try and help others determine what is best for their needs. When I mention drone, I am extremely sensitive to the frequency that exhaust emits. So your level of hearing may be different than mine.
1) The full stock set up with the 22" magnaflow provided great numbers. The hp and torque increase from stock was 8 and 14. Sound was a little louder than stock and there was noticeable drone to me at 58 to 62 mph. Bang for your buck can not be beat here. Once again I ONLY changed out the muffler. Part number 12586 (satin finish stainless) or 14586 polished stainless). If you want to go with the 18" magnaflow part number 12256 (satin) and 14256 (polished).
2) Maganflow catback single exit provided the best gain period with the STOCK titan. The numbers on the website of 18 and 22 were factual peak to peak numbers. Not a play on numbers like many manufacturers do and show how much you gained at a certain rpm when you actually gained on 2 or 3 peak horsies. One odd thing that needs to be realized with this set up is it uses the STOCK Y-PIPE. I tried this set up with a custom 3 1/2" Y-pipe and lost a lot of torque. drone once again, is pretty noticeable at speeds mentioned above.
3) Gibson Swept Side is in my opinion a great all around exhaust for a couple of reasons. One it does provide medium gains in hp and torque. But two it has a great sound with almost no drone. It is louder than stock at WOT, but at start up it is just a deep tone that sounds great. But if you want something that is loud and mean, this is not for you. Gains 12 hp and 14 lbs.
4) Borla dual. It sounds really good to me. Cruising speeds had no drone, drone was only around 45 mph. the gains in hp were comparable to the gibson (12), but the torque gain was very minimal (9). But it is a very clean sounding exhaust that will please MANY and the finished look is very nice.
5) Flowmaster 40 series did not stay on for an entire day. Drone felt like my head was going to cave in. I greatly apologize for not being able to tolerate it to give a full evaluation, but the drone was heavy between 40 and 70 mph to me. And that is where I drive 90 percent of the time.
6) Flowmaster 70 series. Very good sound. Not to loud, drone was minimal around 1600 rpms. Provided nice hp gains that were equivalent to Gibson and Borla (12 hp and 8 lbs of torque), but once again the torque gain was very minimal. This exhaust at wot was definitely able to turn some heads with its volume and I did notice a couple of pops after going WOT and then letting completely off the gas. So it performs like the Gibson and Borla but has a little more agressive sound than both of them.
7) The JBA provided the best gains AFTER the header install. I do not have perforamnce numbers with the stock exhaust manifold, because I purchased this system AFTER headers. Previously the Magnaflow had the top gains hands down, but after the headers, this one etched out on top by 4 hp and 6 pounds of torque. I think that JBA did a good job matching their systems up. One thing that is interesting though is the muffler that came with it was a K & N muffler. The Y-pipe is smaller than ALL OTHER catback systems at 2.5"...EXCEPT where the bend in the tubing is and at the Y. The bend in the tubing on the drivers side expands to a little under 3" and then shrinks back down and it seems to act like a velocity channel. And the Y has two 2.5" pipes that come together to a 3" collector. There is some drone at 1600 rpms does not matter the speed, but it is definitely tolerable to me. This is a fairly loud agressive exhaust but is still not up with the Flowmasters or Bnaks.
I have another one that I will be adding the dyno numbers on in the near future. I got a magnaflow 2.25" dual in/ 3" single out muffler and ran two separate pipes to the muffler. Just in front of the muffler I put in Magnaflow resonators to help quieten down the truck. So I no longer have a y-pipe and it is set up like the 2007 Titan exhaust but with a wide-open magnaflow. I am now producing the best times the truck has ever produced and am very happy with the sound of it. The extra resonators did help reduce the in cab noise and drone is acceptable for the first time since adding the long tube headers.
So one conclusion that I was able to come to is that the 5.6 loves small pipes. That is where the low end torque comes from as does the max torque. It is funny that the 3 systems that produced the best numbers (hp and torque) used the smallest diameter Y-pipe and 2 of those were with the STOCK Y-PIPE and the other has the same diamter as the stock y-pipe. The dual systems lost speed in the lower range (below 40 mph) and I am convinced that is because of the minimal torque gains and I believe loss of back pressure. So if you want pure sound, the duals are the way to go. But if you want performance, the single exits with the smaller Y-pipe proved to be the best. But if you must use duals, use 2 to 2.25" pipes.
This was done on a Dynojet Dyno and times were tested with my Beltronics FX2 accelerometer.