I have a 1989 E350 motorhome with 65k miles. I thought I needed a tune-up but it is more complicated than that. With new wires, plugs and now one new injector I have problems with #6 and #1 firing plus the others are loading up badly. #6, where I put the new injector, has a spotless plug. No gas gets to it. #1 is so wet the gas drips off of it. The other 6 plugs are firing, but sooty black. The injector harness is in good condition. Good, even, compression all around. Any ideas anyone?