conking out after i turn it off

[BoatsRcool]

ok this happened when i put my muffler on backwards, but it has been fine after i fixed it, for like 8 months. now, sometimes, when i turn it off, it will struggle to keep going, then just cut off. whats wrong!!

also if i floor it HARD then it just boggs down still, i have made it not as bad with a new MAF and etc. but its doing it again.

 

[jimbo74]

that is residual back pressure... it is normal...especially with an aftermarket performance muffler... mine does it really loudly... flowmaster non delta 40