I bought a troubled '91 ragtop that had been "modified" by a young kid and his friends. They were hip-hop types who wanted to do donuts at the local schoolyard. I bought it for a decent price, it ran pretty good but had many problems. I drove it home and began fixing them one by one and the car is looking MUCH nicer, I am able to fix things like the clutch cable, the shabby interior, sway bar links, exhaust rattles, etc., but I am pretty weak when troubleshooting drivability problems. The car has a fairly healthy engine, it has good power, I am fixing various fluid leaks one at a time, but the idle is very irregular, and I am looking at obvious things that are not right. Here is an obvious one: (I tried to post a photo but don't see how to do it)--Between the air filter and the big cast intake plenum is a piece of aluminum irrigation pipe in place of a FI part. There is a good sized electrical plug, the part is just gone, replaced by the piece of aluminum pipe.. Is this missing part the MAF? How can any engine run while a sensor like this is missing altogether? Do I go to Ford for a new one? Can I get a good one from a wrecking yard? How do you test a used part like this? Can I just get one, plug it in and drive away happily?