Since I've bought the van, it always run a little rich. = Thinking my problem was caused by the cracked rear exhaust manifold, I had it replaced...along with the muffler and the o2 sensor. The PO (or = PO's mechanic) had messed around the the AFM (spring tension) and can't get = it back to spec for anything. When I test the voltage at the o2 sensor I'm = getting about 0.9v...if I try to lean it out, it runs like crap (lean = misfire). If I set it where it idles good, it runs too rich and can't connect the o2 = sensor to the circuit or it will run even worse and has a total lack of = power. Is it normal for these engines to want to run so rich??? I borrowed a = friends AFM last night and it seems to have smoothened out the power band but = still has a lean misfire. What should I check next?

BTW: Unplugging the fuel pressure regulator (and blocking the = vacuum hose) has no effect on the mixture. Can an increase in fuel pressure = cause the engine to "want" to run richer???

Recent tune-up, new air filter, timing and idle are set = correctly. Temp sensor II seems to be in spec. The Bentley manual hasn't been = too much help without access to a "sniffer". Fuel economy = has been somewhat poor up to this point (about 15 MPG). Any help would be = much appreciated at this point.