Any suggestions?
The car stumbles a bit around 3k rpm under acceleration. It has 115k and otherwise performs well. Start with a change of spark plugs before putting in an RSR engine?
Thanks.

Maybe 02 sensors, MAF, etc? Not sure but you'll get some good feedback on this board.

one cylinder isn't fireing correctly. I have changed plugs, the O2's, vacuum lines, spark plug wires, and ECT sensor and it still does it. Next on the list is to check motor/transmission mounts.