Did you replace the actual DME (the silver-colored Motronic computer made by Bosch - it's about 8 inches square) or just the black DME/fuel pump relay which plugs in aboove the fuse block under the das above your left foot? My 1983 944 had this same condition. At first I tested fuel pressure at the rail and that was good. Then I replaced the DME/fuel pump relay (the plugs were blackened and burned looking around the edges). Still no start. Then I replaced the speed and reference sensors (Pelican and ******** AZ have them inexpensively) because the reference sensor tested bad on my multimeter. No change. Then I replaced the ignition coil (it was leaking oil), spark plugs (because testing with my spark plug tester showed no spark when attempting to start the engine the blugs were very worn and fouled and could have caused damage to the DME resulting in this problem), spark plug wires, distributor cap (worn internal contacts) and rotor - basically the whole ignition system. Still no change. I was about ready to give up. So I pulled out the DME, opened up the case and started testing the internal components for continuity using my multimeter. I found several resistors and other components lacked continuity. So I ordered a used DME (from
egrafton944@hotmail.com but you can also get rebuilt ones with a 5 yr warrantee from ecudoctors.com) , plugged it in and VOOM!, it started right up! This video and the comments below it proved helpful in diagnosing this process.
https://www.youtube.com/watch?v=1WuZuPcVuqM&list=LLxnIXt-NuNTQNX24m66jECw&index=2&t=199s