Ive decided to run straightpipes on my 97 Z71 with stock cats, and thrush glasspacks. what is necessary for me to do with the o2 sensors? ( install extras? relocate the old ones? ) and does anybody know the size of the exhaust pipe before the stock 2-1 muffler?

And i would like to clean the sensors too... ive read a couple different ways, but not sure which would work the best... heat with propand then cool in water, wire brush, sensorfriendly spray from parts store, soak in gasoling ( is this even okay for the sensor? ) If anybody has a way that worked good for them. please share it with me