After doing more checking on the 88 vette vats system, It appears the vats system is in the prom of your ECM. GM used proms up until 1995. It's programmed to be enabled, only way to change that is to replace the prom to disable the program. Looking at hypertech proms they don't discuss vatts in the system. Might give hypertech a call or email and see if a performance chip with vatts disabled is available. There are a few companies that make chips. Jet for another. I can only guess if your fuel pump is bad or is it vatts?