Since my last post I've done a bit of research which lead me to try unplugging the MAF sensor. To my surprise with the sensor unplugged the van shifts normally, accelerates without bogging down, and sounds normal. When I plug in the sensor the van doesn't shift correctly, the engine bogs down when the accelerator is pressed more than a quarter of the way to the floor, and the engine makes odd sounds. The MAF sensor is less than a year old and I have tried cleaning it. When plugged in, the MAF sensor does not trigger the check engine light. One thing I should mention, both canister catalytic converters are hollowed out. Would these canisters impact the vehicle running correctly when the MAF sensor is plugged in? If not, and if replacing the MAF sensor doesn't resolve the issue, any other idea what the problem could be?