My late grandfathers 86 gn has been acting up and i cant seem to find the problem with it. It has been sitting since 1993 and in the past few months I got it inspected. It seems to drive fine under light acceleration, but as soon as you accelerate hard, the car stumbles and just shakes and refuses to accelerate. In the last two days, i replaced the spark plug wires and spark plugs with copper ones instead of platinum. I also replaced most of the vacuum hoses throughout the engine. I should note that even after i replaced the spark plugs and wires, it still seems to have a miss (you can hear a putt...putt...putt) coming from the engine. From the research i've done, most people think the next step is the coil pack and ignition module. Also, the injectors in the vehicle are original and to the best of my knowledge have never been replaced. I already replaced the maf a while back and did the tap test at idle and noticed no change. Any response is greatly appreciated