89 E30 with M20 intermittent misfire

Hey everyone my car is been having some problems lately... Mostly when Im crusing on the freeway or under high load the car misses one cylinder. I pulled the car around and started to do some diagnostics. I started at the Ign Coil and ohmed the primary and secondary circuits .53 and 6100 ohms which is normal. I pulled the spark plugs (E3's which could be the problem IMO) wires (almost 0 ohms on all which is normal), and the rotor (cleaned the posts up). I put it all back together and test drove it. The problem was still there but not as apparent... The problem feels like a ign cut because its so sudden and not just a loss off power like a fuel cut problem. Im going to buy some NGK-R's on Monday to see if its those ****ty plugs but other than that Im at my wits end and would appreciate and input or help. Thanks!!!