I have just got my car out of the shop having new plugs, and optispark put in and I am still getting what sounds like an exhaust backfire between the shifts. It does it on upshifts and downshifts but only at WOT. On my other car I would get backfires between shifts every now and then when I was spraying because it was too rich. Could this be the problem. Could there be a problem with the Cat? I also have a DTC 18 which was somthing to do with the injectors, I am not sure what to do to get rid of that light, or if that may have anything to do with this issue.

Thanks for the help.

 

I tried unplugging the MAFS last night but everything still ran exactly the same. Although it did seem to run a little leaner when looking at the Scanmaster.