Magnaflow Cat back gets two thumbs up!!

denali_dave · April 19, 2003

I just installed the Magnaflow Catback for the Denali. The truck has two cats, one from each engine bank, going down to a two inlet, one outlet muffler. The magnaflow duplicates this. The mid pipe that connects the two cats to the muffler is about 3 ft long. The size difference between the stock and magna even here was about 1/2" larger in diameter. What I like the most is their muffler, polished stanless, fully welded and when you look into it, you can see straight through. No bends to interrupt or slowdown the airflow(read,backpressure). Its not like a Flowmaster that redirects the air. the two inlet tubes seemlessly y down into the outlet, which is 3 " all the way to the rear. Its finished off with a nice 4" chrome exhaust tip. The sound is deep and powerful. Seat of the pants the 5.7L's rpms climb faster due to the less restrictive exhaust and seems to be making a 15-20HP difference. Well worth the 375.00 I paid for it. Next is a Superchips programmer. After that, it all must be selective. Its very possible to change the air intake and it not perform well with the reprogramming. Will advise on this and wheter the exhaust gives me any mileage increase. Currently 10.3MPG in the city and 14.1 on the Highway

cowboy02 · April 21, 2003

Im supprised that you are not getting 15MPG with your denali before these mods. Have you gapped your spark plugs lately? Replacing them with some good quality plugs might boost your mileage up also.