Until I could eliminate the possibility of something being wrong with the rotating assembly and pistons, I'd let that ol girl sit. Sounds like what my 85 Firebird was doing. That ended up being a spun bearing and scored crank.
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WizAire CAI w/9" K&N & HV3, 2.5" d/p w/h/f cat, Cobra CB, PowerSlot slots w/Hawk HPS, GR-2s, GMPP handling kit, NextLevel STBs, Pilot Sport A/S Plus tires.
98 L36/MM5
RaC