its a plug to adjust the timing for different sea levels. basically if the car supposed to run on 87 from the factory and pings under load, it will retard the timing 2 degrees and get rid of the ping. mess around will it. it doesnt hurt if you leave it in or out. it wont bring up a code either, but dont quote me on that. they also call it "octane shortening bar". leave it alone if it runs fine. its onl;y there to get rid of detonation, and gas qualities that cause "ping".
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Cobra brakes are on! Finally.....
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