Need ideas on this one

I have added a rebuilt turbo ,fuel pump , catalitic converter, Diagnostic,and it still looses power after it run about two hours. Let it sit awhile and itstarts and runs fine for another two hours. I'm out of ideas as wellas money. Help!

Connect a fuel preasure guage and tape it to the windshield. Take it for a ride. When you loose power check the fuel preasure. Connect a scan tool that will read engine sensors. take it for a ride. Read scan tool when you loose power. If the scan tool has a record button, Hit record and compare readings before and after.