thanks for the info guys, especially oldbull.
we did a comp test on the engine with it cold and all three cylinders were right at 250. so we know that it is not a piston, ring, cylinder wall problem with the far back cyl.
All the varrying differnt compression readings that youve been getting tell you right off that it's just a sticking ring problem and not a mechanical problem. When teh rings can't flex freely in their groves, strange things happen. Once you get it all cleaned out it should take care of the problem
when I first got my truck, the back 2 were reading around 135 and after the auto Rx they were all up over 400 psi, and it was probably one of the milder cases I've used the stuff on.