1993 Indy Classic fuel injection issues, motor slows down Options

[slednut]

OK this is kinda hard to explain, i have a 1993 or 1994 Indy classic 500 fuel injected, i bought it with a burned down piston, i over hauled it new pistons, crank seals, complete rebuild. Well i got it all back together and it runs great ! it will sit and idle for ever, sounds great, will rev up on the stand BUT when the throttle is held in one position for to long it acts like it wants to die out, flutter the throttle and it picks up and goes like a scalded dog, but hold it in any positoin for any lenght of time and it slows down....

Here is what i have checked, there is no codes on the computer (no blinking light) there is fuel returning to the tank, its not a steady stream but its there, i checked the fuel intak filter in the tank its clean, i will replace the inline filter tonite, but other then that im clueless as to what to check next.....

Thanks for the help on this one