Thanks
If you can believe this I replaced the air cleaner and instantly better engine performance, duh? The engine runs better but I still hear and feel a flat spot around 2400rpms which looses smoothness. Let me see if I can describe it. Rev the engine when warm, and all four cylinders sound clean, then at the same rpm the exhaust sound breaks rhythm and engine rpm slows. I have several books for this Trooper, to me this does sound like poor injector spray pattern or wrong pop off pressure. I like to have alternative sources of info, so yes please, post the link.
I have read through the factory manual on cleaning the injectors. I think I'll invest in the proper tool for testing the injectors. I think someone posted a link to a Harbor Freight or Northern Tools injector pressure tester that'll work. But finding it again... <img src="/forums/images/graemlins/baby.gif" alt="" />