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Well, incase some of you remember, I bought a 91 with a consistant misfire at 4500+ rpms. The car is stock except for a 2.5 catback and an intake pipe. After replacing about every possible thing I could think of, I've started to come up with some success.
I did a boost leak test and found the reducer from the 3" hard intake pipe to the turbo had a hole in the back side of it, along with a little corrosion on the outlet of the IC. So I fixed these by clamping the IC pipe lower on the outlet, and putting on an old factory intake pipe. Still the problem wasn't better. Then I decided since the stock intake was back on that I'd re-run the evap hose to it as well as removing the breather filter on the valve cover and just running a hose to the intake pipe (both normal, stock vacuum lines). Anyway the problem is now considerably better. I can run the car all the way to redline with a just a couple of lean pops every now and again, but they are nothing like the consistant ones I'd get before.
According to my pocketlogger, the low fuel trim is back down to 110% from being previously maxed out at 139 and the other trims are comparable at 120 and 114, mid and hi. I've noticed however that the lean pops I get close to redline are causing knock which leads me to believe there's not enough fuel. I'm going to try a couple of things to get more fuel and see if I can get rid of this completely.
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