I just scored a complete holley TBI unit tonight from craigslist for $50 that uses the newer style Delphi bottom feed injectors. The unit is actually for a 4.3 S/T truck, but the only differences between it and one for my application (89 Firebird w/L31 vortec engine and original L03 TB and injectors) are the injector flow rates. The bores are 2" and the unit is rated at 670cfm just like all of their other TBI units save for the 2.8l model. I am relatively unfamiliar with the Delphi bottom feed injectors, but from what info I can find they may just be perfect for my application. I have posted in a few other threads that I have a walbro 255lph high volume AND high pressure fuel pump that overloads a factory fuel pressure regulator. I have been running with a base fuel pressure set at around 30psi, but suspect that I have been dealing with a lot of fueling issues due to running the O.E. TBI fuel injectors at that pressure. From what I can find, these Delphi injectors are intended for and are used in applications with higher fuel presures. The data I have found puts the max operating pressure at 70-100 psi depending on the part #'s and several O.E. applications have them running ~30psi. I am thinking that if this is true then the 4.3 injectors in the unit I got are perfect for my car because the flow rates at ~30psi should be closer to what my 350 needs than the 305 injectors I am using now. I just wanted to get a little confirmation on that info before I go throwing the Holley unit on my car. I noticed that the FPR on this unit has a little cap that is held in place by a little spot that is peened over and am assuming that after removing the cap the pressure can be adjusted similar to the O.E. units. It also appears that the diaphragm itself is identical to the factory units as well. If all of this is true, then I may just have happened upon an excellent piece for my car. If anyone has a little more info for me I would appreciate it as Holley ain't offering up much info on their website although they were kind enough to put up the latency info for these injectors.