So over the time that I've had my car(since December) it would have a day once a week or every other where it just didn't have any power at all. When I hit from 50 it doesn't downshift or anything just coast up to about 70 then kinda speed up. Well over the last week and a half it's been doing like that constantly. My exhaust is extremely quiet while it's like this, and I have. I idea what direction to go in. The only things I have done to my car is a cold air intake, mid muffle delete, cam and lifters were replaced in February(stock still), that's about it please help!