i was @ the junk yard and i was looking at different tbi units on different cars , like caprice some potiacs, and cadillacs , i noticed a differance in the bore size and obviously the injector size /flow , but my question is , are the pressure regulators all the same ? , same goes for the diaphragm .

 

I believe they all use GM 12 lbs for fuel pressure so I believe they are all the same. I doubt attachment pattern did not vary. One exception. The marine TBI units(7.4L) I believe have different springs. As does the 1995-1996 7.4L truck engines have different springs.(26-32 lbs).

 

There are dozens of GM reg part #'s, a half dozen are most common. I think the smaller diaphragm remains the same part, the aftermarket uses 1 diaphragm for 98% coverage.