I did install the flex fuel injectors. The weather has been to bad here to drive the car to test it out though. I have two fuel pressure regulators, the stock stainless one that I believe is set to 55 psi and I bought one that fit the GMC Typhoon, turbo Trans Am and earlier 3.0 gm v6's. It has a base pressure of 45 psi. Bolts on to the stock rail and looks exactly like the factory one. I have it on the engine right now. If the fuel is close on the wideband under most driving conditions I will just leave it on and fine tune the cal. If its a little lean all around I will use the c-clamp adjustment on it. If its way too lean I will just put the stock 55 back on and go from there. I made a small test station and used it to clean the flex fuel injectors before I put them on the engine. I was able to do a crude flow test also. I will get some pics of that up soon.