DIY Exhaust Mod – Gain of 10+ HP!!!

[fishfood]

I can't see spending a grand for a new muffler,especially for the small gains it makes, but always wished the car sounded a bit more aggressive at lower rpms. Drilled two 1/2" holes, one on each side, using a 12" long bit, it made a small difference from idle-2500 rpm. Went up to a 9/16" and it sounds great now! That extra 1/16" adds over 25% more to the drilled cross sectional are, and it makes a big difference. Car sounds great at idle and normal cruising speeds, no resonace at all. Above ~3000 can't tell a difference at all, which is fine with me, it has always sounded good at higher revs. Just use a good sharp bit, push slowly and spin the drill slowly until the bit bites. The 9/16" bit fits tight on both sides as you put it in, but this helps guilde the bit and I didn't have a problem slipping. Thanks for the tip!