OK, here's my prob. I have a ls teg with an Injen CAI and a hi-flo cat with 2.5" Airmass Thundermuff catback exhaust system. I have noticed good gains in the top end where it needs more flow, but it either seems to have lost some power in the bottom, or maybe just by comparison my low end seems laggy. It's been suggested to me that it's too free flowing and a lack of backpressure may be to blame for the slow bottom. So I was wondering what I could do to improve my bottom end. I havent decided on which kind of header i want yet, 4-1 or 4-2-1. I was thinking possibly the 4-1 would restore some back pressure down low helping that and then give me the good flow up to that 4-1s r known for. But 4-2-1 claims to be better for low end power, but i'm curious to think if it might flow too well on bottom and the restrict up top. What do yall think?? Also, I was considering either buying a lightweight flywheel, or having my stock flywheel cut. But keeping in mind that this car also needs to be my daily driver, will a lightened flywheel hurt my reliablity a lot? would a 12.5 lbs still give me decent acceleration, or can i safely go with a 8.8 lbs and not loose too much reliabilty except for maybe a little decrease in gas mileage? What would yall recommed for some increased bottom end power and real quick acceleration?