Hey Spook,

Thanks for your reply. So, I disconnected the negative cable last evening for about 30 minutes. After reconnecting the cable and starting the engine it still had the same issue. I then disconnected the negative cable again and let the car sit overnight. This morning the engine is still exhibiting the same problem. The engine idles fine and runs fine except for the fact that it won't rev beyond 4000-4500 RPMs.

On 'The Volvo Owners' Club' website they write that one of the symptoms of a bad/failing ECU is that the engine won't rev higher than 3000 RPM. They also write that when work is done on the ignition system or the negative cable is removed from the battery that it can sometimes take a while for the ECU to reset to the proper control settings. I'm hoping that that's the case here.

Before I swapped the original ignition coil/amplifier with the newer one I had no issue with the engine not revving to the normal 6200 RPM limit. All of the wiring harness connections to the coil/amp were cleaned this past summer - so that shouldn't be the issue - but I will check and clean them again later today.

If giving the ECU time to reset or cleaning the connections again doesn't solve the problem than the only thing that I can conclude is that the newer replacement coil/amp somehow messed up the ECU to the point that even removing it and reinstalling the original one cannot restore the engine to it's proper and previous running condition. What are your thoughts?