I have an 01 neon es. 5spd man. 130,000 miles. When i'm driving i lose power through every single gear at 4200rpm. The power picks back up at about 5200rpm. I have replaced the air filter, and had the fuel injectors cleaned profesionally. This happens weather or not i have the a.c. on or off or heater on or off. It feels like i go from full power at 4100rpm, and i soon as i hit 4200rpm, its like i have the a.c. on while pulling a large load behind me. Any input will be helpful.

Thanks

 

ecu could be messing with the injection is my guess, there is no other possibility is you pretty much have checked everthing, unless something internal in your engine is messed up and at 4200 it's at it's worse but I dont see that happening becaues you would know something would be up, b/c your engine would be making nosies etc..