1985 Plymouth Reliant will not idle

I have a 2.6L Mitsubishi engine with 450,000 Km on her. I took the engine out of my 1985 k-car and dropped it into a 1988 Chrysler Dynasty body. It has given me years of great service until now. The other day I drove it to work ( aprx 20Km ) and as I pulled in to park she died. It restarted right away, but it would not idle. I turned my idle way up so that it will idle, very roughly. I checked for any vacuum leaks and replaced the intake manifold gasket as it was leaking abit. It helped some but it still runs like a bag of hammers. When the engine is cold it runs fine but as it heats up the idle gets rough. I did a compression test and leak down test and they checked out my compression is running around 150psi in all four cylinders with no loss of compression. Unless I am missing something with these engines that leaves the carb. If that doesn't work should I take the head off, really do not want to as the head gasket is only a year old.