Take the fuel pump apart. Look for a lower ripped diaphragm. It also sounds like your tester is not accurate. 120 is the best the factory could do.
Post #22 is the 88 manual.
https://buggiesgonewild.com/showthre...=105501&page=3
This thread shows inside the fuel pump.
https://buggiesgonewild.com/showthread.php?t=98839