need help guys. my 1990 5.8 is running really rough and rich,i mean rich!! this just started about 3 days ago. egr valve, fuel pressure reg. iac valve, tps, and everything related to air- fuel has been replaced exept fuel pump and injectors. it sounds like it is missing but when i get on the gas it responds. it will also start jerking and at hwy. speeds. steve 83 mentioned something about a loose timing chain. i tried adjusting the timing to see if that help. it raised and lowered the rpm's but didn't help with the missing. also spark plugs and wires and rotor and cap are about a year old. thanks in advance for any help.