I own a 1983 944 and it was running rough. Almost like it was missing or had a fuel problem. I replaced the fuel injectors, fuel regulator, fuel filter, new plugs, new wires. Still runs rough, like its missing or running rich. Low idle. Any suggestions what it could be would be appreciated.

When you say low RPM's do you mean at idle, that low? Two common things are the motor mounts which are common to get worn. When these are bad the there will be a lot of vibration at low rpm and go away when you rev it. The other is a bad balance shaft belt.