Problem with 02 sensor after dump pipe installed. Should I buy new 02?

[Spins]

I had a greddy dump pipe installed. Installer cleaned o2 sensor with gun cleaner. The guy swears buy it. After install I get funny readings from afr gauge. My afr gauge always read lean at idle and cruising and would swing through the spectrum into rich mode at heavy or wot.Now my gauge shows lean at idle and cruisng but disappears at heavy or wot, or so I thought. At night at wot the gauge was dim, barely visable showing into the stouch range. In the day this is unreadable. If I let up at wot the gauge swings the whole spectrum of the gauge to full rich and back again in the blink of the eye,readable. In N I can rev the engine and the gauge will swing the full spectrum, readable. It always did this. I removed my boost control returned to stock boost,same effect. I upgraded the fuel pump and filter about a year ago just before swap. I know the afr gauge isnt accurate for tunning but this bother me now. Would the greddy pipe cause the problem or is my o2 sensor screwed due to the cleaner used? Or am I really running lean here? The rear of my car was always blk around my exh. so before I was running somewhat rich. A new 02 is $70 . I installed a new one of these just after the swap.

[robbbby]

I highly doubt the greddy pipe has anything to do with it. Either the cleaner the mechanic used messed it up or your gauge is just inaccurate like any other crappy narrowband O2 gauge.