I'm still fighting an issue with my port 8.1L engine where it 'pops' under heavy load or at 3500+ RPM's. You could almost describe it as a very very light backfire maybe. But's a rapid pop-pop-pop sound. It's been discussed here: http://clubsearay.com/index.php?threads/8-1-power-issue.84318/page-5 however it was somewhat buried in a long thread and I didn't want to keep adding to the OP thread so I'm starting my own. In a nutshell, I've replaced plugs, wires, fuel filters, oil (not related) and now the fuel injectors. The engine idles and runs flawlessly up to the point of the problem. No smoke of any kind. They engine has 400 very well maintained hours on it. So now what could be failing? I was thinking possible the one of the individual coil packs. Does that make sense? If so, how can I find which one it is? They are very expensive at almost $800 for a set of 8. What other components should I be considering? A friend mentioned the Throttle Position Sensor but I'm not sure how that would cause the is issue. Or could it? If I don't get a clear path then I'm going to have to have my marina look at it and quite frankly I have very little faith in their capabilities.