Hey guys I got my 2 1/2" exhaust system finished with MagnaFlow muffler. The car is a 68 383 cuda 4 speed stock exhaust manifolds. I took her out for a ride and ran through the gears and I get lots of back rap and poping when letting off the throttle. So I added a H pipe lastnight it helped but still there. Before I research other mufflers is their anything thing I can do to eliminate the back rap. Thanks