I need some help:

I installed a Flowmaster American Thunder Super 40 series exhaust system, with dual side exits in front of the rear passenger wheel.

Ever since I installed this system it seems that my gas mileage is in the ditch, and I lost all low end power.
I have to rev the crap out of the 5.3L, and now it seems to be going slower and slower.
Towing a trailer makes the truck fall flat on its face, and my shift points are all changed now too.
The shift kit, which before would snap, now feels like a regular shift.

I had this same issue with my 96TA - is this a Flowmaster muffler result, or do I need to re-program for a low restriction exhaust?

The rest of the truck is bone stock.

What should I do?

 

do like iam fixing to do and ditch the flowmaster and get a magnaflow

 

Its the blowmaster. I had the same situation when I had mine, lost all low end. Ditch the flow for a magnaflow or dynomax or something similar.

 

Damnit Jon, everytime I get an idea of something to do you have the same idea! I have been trying to find a Magnaflow or 2 around here.

 

I might just ditch my flows when I have the exhaust redone, I love the sound but I can't say I noticed any loses or gains with mine. If they a really that bad I may consider something else.

 

nightmare i am going to prolly order a 3" single inlet w/ dual 2.5" outlets and then run them out the back like before or atleast to the back bumper before i dump them

 

i installed that same setup couple months ago. mainly bought it because both of the pipes exited same side in front of the wheel. sounded good, with cats, didn't notice any power gain, felt weaker under 2K. put my cam in and cut the cats for the WBO2 and the Super 40 became the Super Loud. went the next day and had the magnaflow 3 in dual 2.5 out installed.