my sons 97 blazer 4.3 was stalling out while driving and getting like 6 miles to a gallon took it to shop fuel pump was replaced before going to shop cuz gas gage didnt work ran fine for two days then fuel started purging where i dont know but it would stop if you opened fuel cap and it was under pressure or vacuum we took plenum off and sure enough there was gas in the galleys and in the oil so mechanic checked fuel pressure and it was within fact specs and would hold pressure determined a bad pressure regulator cuz it would intermittently leak.i decided to replace the whole injector with regulator.my question is has anyone replaced one i had the cpi but am changing to the mfi is this unit better?

 

mfi is supposed to be better (less leakage problems). It's pretty easy to replace, here's how to on my 98 (if you have the same upper plenum i'm not sure what year they changed over).

Take off intake elbow (or whole intake)
remove cables from throttle body
remove connector from spider and 2 (or maybe 3) from throttle body
remove fuel lines from spider
unbolt upper plenum and remove
Take spider out of bracket (i used a flathead to pry the bracket open a little) and pull poppets out of their holes in the intake.

Installation is reverse.