I did a auto to 5sp swap on a 87 n/a hard top. 145k on the clock and was running fine. Now, it runs like crap under 3k and wont idle. Just dies. Also, when you spin it up easy, it sounds ok, but under any harder throttle it has a rattling noise from the back passenger side of the engine. Symptoms are identical to detonation, but with two bottles of octane booster and playing with the crank position sensor, still no effect on this "detonation". I can't see any obviouse vacuum leaks, nore hear any. I've also tried two different N326 ECUs. Both acted the same way. Any help would be awesome! Thanks so much!