7.3 won't start when engine is hot

99 F350 with 168k, turn the truck off and try to restart and it won't restart for about 45 minutes when the temp gauge shows cold again. I had this happen a couple times last year and it has now resurfaced. I just had a fuel leak repaired on the filter housing, and they also tightened up a bolt on the IPC. New O-rings last year, new engine oil pump, new ICP, new CPS via the recall. Its a real stinker because it never makes the CEL light come on. The issues last year were was low injection pressure at start up so we replaced the low pressure pump, and not enough volts at start up to fire the injectors. Been running good for a long time since then but I definately want to get this taken care of. Any ideas guys?