bucking car over 1500rpm

[Rodoggx]

Hello,

Some background: My 1990 5.0 has been sitting in the garage unran for a really long time ~8 months. Recently I installed some flowmasters, bought a new tire for it, and charged the battery (trying to get it up and running).

Over the weekend I got it all buttoned up and took it for a spin. It ran smoothly- no problems. Two days later and now it bucks like crazy while driving. Its almost like the engine dies for a hot second. It'll stutter and loose 500 rpms but when the revs come back it bucks and when driving on the highway the bucking can be quite violent. It most often dies/bucks over 1500 rpm (under load) but sometimes it'll stutter at idle (not to often tho). No noises. The engine just seems to die, lose the 500 rpm, and then fires again. Doesn't seem to happen at any consistent time interval either.

I was HOPING it was something as simple as bad gas or moisture in the tank. So I filled it up and put some STP gas treatment. So far no change (25 miles later).

So guys, any suggestions?

Thanks,
Roland