1998 Jeep Wrangler Jeep Wrangler barely running

My wife owns a jeep wranger and it is her dads and he did take care of it until he lost his leg and was unable to drive it, then it sat around for a while. Not until recently has it gave us problems though. It Idle's very rough and when she drives it will sometimes (often) lose power and gain power on its own so she has to pull over and shut it off and back on. We have put premium gas in it and ran countless fuel injector and fuel system cleaners. Most recent was seafoam and they seem to work for a little while but then the problems come back. It is also difficult to shift at times and the seafoam helps with that. Im absolutely baffled. Please help.