rich Z

I had a bad air pump check valve that was causing exhaust pressure in the whole hose line. I replace the part and then all the sudden I have massive pinging. Enough I'm affraid to drive the car. I have cleaned the maf and still pinging. I tried a old slp maf sitting around and the same pinging. I checked the mass air sensor plug and it reads 5.0 volts blk to yellow and 11.36 from the battery. Shouldn't it read 12 volts. If I unplug the mass air sensor I get no pinging since it rich up the a/f because I'm running a lean. I have a mass air translator that I have used for yrs to richen up part throttle because with aftermarket lid I have + fuel trims, which used to read +4-6 at part throttle and now read + all the way to 22. I changed the fuel filter yesterday and last week checked the fuel pressure and it's good. I have tested the 02 sensors all and there good. I also tried a seafoam cleaning and added some to the gas.