I have an 82 MC 228 GM 305, Cylinders 2, 3, 5 and 8 are producing little power. Compression is low on all cylinders 130 - 140 psig (engine has a lot of hours) but even. I was out running it last weekend all was normal and it just lost power. Idles OK. When I run the RPM's up to about 1500 it...