A good tach would certainly help. The factory tach in my car is off by 200 rpms at idle and a lot more when I'm accelerating. I wouldn't be surprised if it's off 600-800 rpms when my shift light comes on.
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1989 lx notch
89,000 miles
bolt-ons,stock heads/cam
60'- 2.07, 8.90@78, 13.93@99
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