so i got a mpx downpipe catted and installed it i had the muffler delete it was 2 loud for my taste so i put the stock muffler back on and the car seems like it has alot more power now i have gms1 its also bosting around 19lbs instead of 22 like it did before maybe its in my head? anyone else have this happen? not that its a problem more of just a why shouldnt the no muffler have made it faster?

 

Are you sure you're not just thinking it is slower cause boost is lower? Might be off here but with a better flowing downpipe and no muffler means less back pressure easier to get exhaust out lower boost necessary to generate the same power as before. Just a thought.

 

You're getting more back pressure with MUFF in...that will increase low end torque and you CAN feel that. However, peak HP will prolly be less. I found the same thing when I added a silencer (into Muff end) to my cat back.

 

u dont want back pressure with a turbo car, only on na or supercharged cars. That will not give u more torque

 

You change the torque curve....and you will get more torque at lower RPMs....turbo or no turbo. I know this first hand as I stated above (it's a TC). That doesn't mean back pressure is always a good thing, since you give up high end torque (HP).