It's a cobbled together system with an early megasquirt controller.
Langdon said GM tried to get efi systems to work with injectors on the 250's in Mexico towards the end of their run and couldn't get it. He described them doing exactly what you did. The problem was something to do with swirl. He said they couldn't get the system to not run lean. I suggested the weirs you have in yours and he said they helped but never completely stopped it. Maybe they didn't protrude far enough in and weren't using lumps so the air/fuel was swirling behind the head stud boss? Just a thought.
He also said that in N/A applications the weirs would essentially cut the flow to the individual cylinders in half. With a forced system, though, that shouldn't be as much of a concern I wouldn't think.
I'm not sure how they tested it. Probably something way above what we're able to do. I doubt they just hooked up an O2 sensor or read the plugs but you never know.
Tom and I talked for a good hour about the build. His headers were the first performance part I put on the engine. Really nice pieces that seem to flow very well. Since the intake and carb I can tell the only things holding it back (n/a) are the cam and head but she's still quite a bit faster than stock.
All that aside I wondered about the new systems and their ability to better control things. The GM testing was done in the 1980's and technology has improved just a little bit since then...
