1995 Mitsubishi Mirage Gremlin in the motor.

Dear carpros.
I really need your help. Il try and keep it short and to the point.I recently bought a 95 mitsubishi mirage LS from a old woman for $500 bucks. Body in mint shape, interior in great shape, engine compartment looked clean etc. Test drive was ok ran really good except for slight vibration at idle. So I figured hell it needs a tune up, so I bought plugs, wires, distibutor cap, rotor button, fuel filter, & air filter. Ran great for a couple days then I started noticing the motor jumping, or missing. Sometimes violently, sometimes minor, then it would go back to running smoothly. So I put fuel treatment in the gas to remove any water I was thinking was causing it. No bueno, motor still hicups. Car idles rough when coming to a stop but if I throw it in nuetral it stops vibrating. Couple days ago while driving 65 mph the car I dont know just lost power and dropped down to 50 mph (even with gas pedal still pushed in) then picked up speed again. Car has been cutting off at stops occasionally, but fires right back up. Check engine light just started coming on, but I noticed when I stomp on the gas the light goes away? Tryd to put a OBD2 scanner on it but it wont read codes. Keeps saying "link error". Checked all fuses and they are good. Any help you guys could give me would be greatly appreciated. Ty Danny