Zero_Fx2

I've had my new borla SI/DO muffler on now for about two weeks now. Sound is amazing and I have had a noticeably (way) better MPG rate. I ran straight pipe turn down for a while and it got annoying.

ProZach

no.... no no no. This is all wrong. A performance exhaust setup can have many benefits however slapping a new muffler on will only give it a different sound and MAYBE .5hp more... MAYBE

trust me, i was a sceptic until AZFX4 and lowered4life took my muffler off and had me run straight pipes, and oh hot DAMN does it sound good.
when it comes to straight pipes vs. straight swapping OEM muffler for aftermarket "performance" muffler there is no comparison. all that either of them does is provide a different sound.
want my advice OP? pull off your muffler for a day and drive around. if you don't like how loud it is then swap an aftermarket magnaflow in instead.

really? could you please prove the above statement?

Sweet Willie

what did you guys hook the O2 sensors too? any info will help? thanks willie

GrnMachine210

If mufflers increased performance than why don't nascars and other race cars have them? I could kind of see where they might decrease performance but that's where a custom tune would easily fixed that. Just my two cents

jerrybizzle

Leave them in place with the cats. No o2 sensors in muffler.

2008f1504x4

Back pressure can really be over rated.. Now I know a drag car is something of another breed then our trucks but they do not run mufflers ... Just open headers... Hell a guy with a 98 gt had a full aftermarket exhaust and also had electric cut outs he did a few seperate dyno pulls and made more with the cut outs open...