Have not used fuel pressure gauge while driving. After 2 or 3 seconds of wot, it starts stumbling.
Secondarys are opening fine, I can feel them as there's a point where the end of the primaries where the secondary linkage needs a bit more foot to swing them open. Linkage is adjusted properly, am using the bracket off of the 2bbl 400 and a custom 2 hole 2 piece spacer to adapt the carb. I didn't want an open spacer due to the weaker vacuum signal, and a 4 hole was too shallow, with not a smooth transition from spread to square. I haven't blown down the fuel lines yet, but I just put in a new pick up and sending unit, a few months before I switched carbs.
I would not attempt to bring my engine up to 4000 rpm w/ no load. Too many things can go wrong. I've personally had engine component problems (when I was young and stupid) from revving engine w/ no load (possibly broken piston or ring, no compression and severe oil blow-by), and was close by my buddy when his fan blade broke off while revving engine in the driveway.