Man, what a rough story. We went through a lot of the same stuff last year on my 96. We changed about every sensor on the thing. Cleaning out the throttle body and everything connected to that helped for a while. We did a compression test and determined the #2 cylinder wasn't firing correct. We pulled the head which was a pain, but not as bad as I thought. You have to take a LOT off to get it out, but most of it's pretty straight forward. You can never take too many pictures. Turns out, the valves on the #2 had a lot of buildup so they wouldn't seal right. Not sealing right led to more build up and the cycle continued. For us, we decided to get a stroker since the engine was getting up there in age anyhow, and we embarked a whole new odyssey. The shared gasket for intake and exhaust is pretty easy to do. We swapped to the 99+ intake and headers for not too much. You might check the neutral safety switch - it can get cleaned out and not replaced and that might help. Not that we have it all together and running yet, but I feel your pain.