my car just recently got fixed for having two bad oxygen sensors air pump and the cats a couple days later the service engine light came back on? I am hearing a ticking noise from the engine and the oil pressure guage is running at 3/4? whats goin on? 2000 black ss

 

After the work you describe I would have guessed a loose plug wire, but the oil pressure is a possible sign of a lifter. Get the car scanned and see what code it is throwing.

 

Or maybe an exhaust leak on one of the AIR tubes.

What do you mean by "oil pressure gauge running at 3/4"?