I need some mechanical advice for my 2002 ford windstar?

My 2002 ford windstar started acting up around a month ago. We're leasing it from easy car credit and our residual is due in august i want to keep this van as we have already replaced several things on it. Okay first off the problems so far have been it hesitates and rough idles. We keep getting codes back for misfires in cylinders 2 and 6 which is probably causing the hesitations and rough idling. Also in the last month we have had the check engine light come on a few different times. Mostly for the various times it detected a misfire but the other codes were for low egr emissions and a faulty crankshaft position sensor… We have been taking it to a local repair shop and each time get it back and the misfire keep happening. We replaced the ignition coil the spark plugs then the spark plug wiring. Finally got tired of messing around and took it to the ford dealership for a diagnosis. As far as they can tel its one of two things or could be both. They want to take apart the Egr system and check for carbon build up and replace the gaskets in # 2 and 6 first and if that does not clear it up then the other option is a faulty powertrain control module. Now i know i have had trouble with that for as long as i have had the van because our abs and brake light go on and off as they please i just do not know if it has gotten worse. Any advice on fixing this problem or comments would help thank you

A friend of mine had a windstar, and it was having similar issues, he ended up replacing a cam shaft position sensor, and that seemed to help. Before that was replaced, we changed the intake gaskets, EGR valve, and all the plugs, wires and the coil. It was better, but still not perfect. Hope you can get it figured out.

Well they said it was one of the 2 or both. Hope they were right