I just replaced the R/H ignition bank (cassette) to stop the #1 misfire that my shop told me needed to be done. No change. Their laptop shows only #1 cyl is misfiring and shutting off the injector after it recognizes the misfire. When I idle at 1500 or greater rpm's it runs perfectly, let it down to idle and it misses. Is it an injector leak? Intake manifold leak? HELP ME, this is getting very expensive very quickly...Thx