Car acts like it has a misfire under load

I have both my coolant temperature sensor and sender now. When I replace them I will check the injectors. I would just think that if the injectors were bad I would get a misfire code or that it would misfire whether it was cold or warm.I wouldn't think it would run fine under 50. It doesn't seem like it starts to become a problem until I'm over 50 mph. Then once it starts it just gets worse. At this point I'll try anything.

Well CARDIODOC. Not 100% sure but after throwing parts at my car for about two months I replaced the coolant temp switch and sender and my max idles well and after taking her on a pretty thorough test drive pushing her a little harder than I typically would, the coolant circuit may have been the problem. I don't want to get my hopes up because I hadn't checked the injectors yet. ( Need to get some replacement o rings first) I did check all my vac lines and my intake though and no leaks. So hopefully this is a victory. Give everyone an update in a week.