i have a gsr motor with 402 crower cams, and full ferrara valve train. it started to drop in rpms when i tried to hold it a a steady rev. So when I try to hold it at 3500 it would drop about 500 to 1000 rpms and go back and forth . so it would fluctuate between 3500rpm and drop 2500rpm and back to 3500rpm. it doesn't do it when the car is cool, only when it warms up. the tps is fine, only code im throwing is o2 sensor but it has never worked, runs fine except for that
does someone have an answer for me?

 

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