I have a 98 neon with the double cam engine. It runs great but idles like crap. Check engine light was on, found a code for fuel system rich. Hooked up a scan tool and looked at the fuel trims and the long trim is pegged at -25%. I replaced the up stream o2 thinkin that was the most obvious and it still runs rich. I checked for a vacuum leak using the throttle body cleaner trick and spraying everywhere possible while reading the trims and could not find a leak. Checked the coolant temp sensor and its reading correctly, checked intake air temp and its reading right. I even tried pinching off evap lines from the purge valve thinkin maybe it was suckin gas and nothing. I also unbolted the converter pipe at the manifold to see if maybe the cat was starting to plug, started engine and read trim and still pegged at -25%. Anybody have any ideas? The car has a manual trans and has 137k miles and fresh from colorado to now cleveland, very clean car by the way lol.