With all the talk throughout the various forums about Cat Back systems and such I thought I would throw in some information that people don't normally think about as well as my observations with my own install. Your experience may vary.
About two weeks ago I decided to break down and get the TRD CatBack and I've been very happy with it so far. I did it not so much for the WOT power that people usually buy these things for but more for "personalizing" my truck a little more since I see so many on the road these days in my area.
Here are some things I noted though:
Everyone talks about gas mileage. I commute 70 miles round trip per day in California stop and go commute traffic. I don't usually do any other driving M-F other than to/from work and I averaged about 18-19mpg with the occassional 20 from time to time. After adding the CAT the first 4 tanks of gas I've put in have consistently been 20-21mpg and I hit 22 at one point... best I've hit so far. No biggie. Every little bit counts.
I definitely have noticed an increase in power. It's not the kind of power that will "win races" but more the kind of power that smooths out the ride a bit. When traveling at 50mph and accelerating I find that I no longer get that bit of hesitation that I used to. I drive an automatic and when I'm about to punch it and pass a slow truck up the grade I drive I always drop it into 4th first anyway so there's no transmission lag from gearing down. The overall power band seems to be smoother though and heading up the grade the truck doesn't "bog" as much in D going uphill. I'm hoping the increase in the higher RPM's will help some when I start camping season this year with my trailer.
DECELERATION (Engine Braking):
Not something one usually thinks about but as I mentioned I pull a decent sized trailer and I use engine breaking frequently. Although I haven't pulled the trailer yet since installing the CAT I have noticed that engine braking efficiency has been decreased. My commute consists of going up and down a fairly decent grade and I regularly drop it into 4th going downhill to stay with traffic and save the brakes. I've noticed though that since installation of the CAT that I'm not slowing quite as fast or as efficiently as before and I'm touching the brakes a bit more than normal. I'm sure that this is due to the fact that by design the CAT is supposed to reduce back pressure and that one factor in using engine braking is use of that back pressure. Hasn't really bothered me though other than the fact that I've noticed. We'll see what happens with the trailer hooked up.
Ok had to throw this one in because everyone asks for sound clips and stuff regarding various setups. Sorry no clips but I'm sure there are plenty out there to find. I didn't buy this thing for sound but here's my impressions. I think it has a decent "growl" although I wouldn't call it a growl but more of a deeper rumble. Definitely seems to lose it's voice at spots through the power band. For me... at about 48-50mph in D there is a slight drone that bothers me although no one else that rides with me has noticed. People are always worrying about this thing being too noisy in quiet neighborhoods as well. Umm.. no way. My wife didn't even notice a difference and she notices everything I spend $$$ on.. Granted she didn't notice the nice shinny exhaust tip but she's not much into cars and stuff. I will say though that jumping on it there's a nice non-ricy sound that has gotten me a few looks from the ricers that think they're going to race me off the stop light. I think they're surprised at how quickly these trucks go. They do that though even without the CAT.
Anyway.. just some information and thoughts on my experience.