Hey there, I recently bought a 2000 Chevy Express 3500. Awesome shape, good deal, driving me nuts trying to find a mechanical gremlin. It has an occasional misfire, known when I bought it. Drove it about 200 miles and it started getting worse, check engine light came on misfired quite a lot so I took it to a good mechanic I knew....His computer told him MAP Sensor and Air Flow sensor. He replaced those, and the old ones appeared almost melted. Drove home, did the same thing. Hauled it back to the mechanic who spent 2 weeks looking and testing but didn't find anything else. Did a global reset, it drove fine--for about 100 miles. Battery light came on for alternator and check engine light came on, giving P0175--rich fuel mixture. Took it to another experienced Chevy Mechanic who got a similar van and swapped known good parts to try to track down the culprit. He did discover the fuel line wasn't advancing the fuel and replaced a small vacuum I believe in that (I think, hopefully that makes sense). It seemed when he drove it with the dog house off, it drove fine, but with it on and when it warmed up it would misfire on various cylinders. He heated the computer to see if that was causing the issue, and was convinced that wasn't the case. Eventually he didn't know what else to try and gave up. I tried a 3rd mechanic and had him replace the O2 sensors, as the check engine light still gave the "fuel running rich" P0175. Didn't help. He suggested switching out the Distributor cap and plugs, which he did. Still runs poorly. I'm $2000 deep in repairs and getting to my wits end. Any suggestions?!