I just purchased a 93 stealth rt manual trans,it is all original and has 28,100 miles on it.When it reaches 3500 to 4000 rpm it bucks pretty badly(under 3500rpm drives perfect) after 20 to 25 miles it corrects itself and runs perfect.I took it to a dodge dealer(for 2 weeks)and they couldn't diagnose it,so I sent it to a mitsubishi dealer as well and they are stumped too.The car is a one owner clean carfax(retiree owned since new)any help or thoughts would be greatly appreciated.Thank you.

 

Since it sat so long, it may be the fuel pump filter being clogged. I would also check the engine computer as well. They can go bad over time.