Ford F150 Help please!!!

i have a 1985 ford F-150 fuel injected 5.0L V8 and it runs well when the weather is cool and when it has been sitting for a while but as soon as it warms up or it gets hotter outside it starts to act up ... it surges between 20-30 and runs fine after 30 till it hits 50 klicks.. then it wont accelerate until it slows to 40 again.. anyone have ideas? already replaced fuel filter, cleaned injectors and fuel pump.. we were thinking maybe the TPS .. but any other ideas would be appreciated

Thanks.

I'm sorry that I can't help with your truck problem, but I have been looking for the fuel filter and can't seem to locate it. Same truck as your's. Does it have an inline filter or is it the canister type? and where is it ? Any help would be great. Hope you find out what's wrong with your's.