2000 blazer engine cuts back at 4000 rpms

I have a 2000 blazer that quit running , pump was bad , filter was stopped up , installed a new inline pump [ 100 psi ] and filter . Also I have installed new plugs , dist. cap , rotor button, air filter and a new map sensor. Now I have a problem when you rev up the engine to 4000 rpms it shuts off until it hits 3000 rpms and then it revs back up to 4000 rpms. It will do this either sitting still or going down the road . Runs good below 3000 rpms . I have installed another computer and did the 30 min. relearn for the pass key . Fuel pressure is 52 psi . There are no dtcs stored in the computer . I was checking the CKP System variation learn procedure and I think this might be the problem , it might pay me to drive it to the chevy dealer and get the computer reflashed , what do you think ? Also the longer you run the engine and let it set idling it will start shuttin down on its own , after 2 or 3 restarts it will not hit a lick until you let it cool off. I have all of the factory manuals and a snap on scanner and I have checked all of the "Typical Data Values" and they check ok . Any help would be great. Thanks Jim

How did you modify the pick up tube in the tank? The inline fuel pump will not pull sufficient fuel volume through the old, existing pump without modification. Your 100psi pump pressure is about 10% too low. The spec on the original equipment AC Delco pump is 108psi. Very important to have the correct fuel pump with this fuel system. If pressure is too low you'll have starting problems. If pressure is too high, the life expectancy of the fuel pressure regulator will decrease. If volume is too low, you'll experience problems at high RPM. Key on, engine off, fuel pump running, fuel pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the pump shuts off.

Why did you replace the ECM? CKP relearn will set a code if there is a problem. What DTC's are in the memory file and also in the history file?