flat response in engine

My 1988 d/l has a strange problem. At cruise it will tend to miss or buck. just a slight increase of throttle will pick up and run fine until cruise is again reached. Have replaced ecm,throttle body and fuel injector,tempsensor. no codes showing. Haven't checked throttle position sensor yet. Been to busy trying to replace head gaskets and valve job on *&^%$#@! mazda mpv.

Have you tried replacing the fuel filter and sparkplugs?

Have you tried replacing the fuel filter and sparkplugs?
Plugs are new but I don't recall when fuel filter was replaced. Will also check fuel pump output but it does run fine under heavy throttle.

i'm having the same problem with my 93 Loyale. it will run fine but when cruising it will feel like its cutting out or missing.....spark plugs and fuel filter changed 8/05 and everything seems fine, other than this.