I had my best ET thru manifolds. I added SLP 1 3/4 headers and never went faster after MANY slower runs. I added an AFPR and tried to dial it in but got as fast as 13.608 on similar 60fts in good weather but I didnt come close to shaving off atleast a tenth or better like I had hoped. Im running a stock chip right now but if you need to add an AFPR, chip burning software in addition to headers to realize any potential then the converter is even still a better investment IMO. In my case the manifolds werent nearly as restrictive as I had thought the best $ I spent so far was BFG drag radials and the SLP 2k stall converter, cooler and shift kit it really woke the car up.