I have a rotary performance fp 1600cc secondaries,
sx regulator. These are fed thru stock fuel lines.
Base pressure is @40psi. The car will surge slightly
in 4th gear pulls. A/f is steady but pressure will
begin to fall from peak of about 4.5 bar. Egts are
below 800c . I suspect limited flow or maxed out
fuel pump. This is at @ 16psi and I am around
380-400whp at this level. What do you guys think
is going on?

 

fuel filter and/or pump is maxxed

but i hope you aren't doing this with a stock pump, if so, shame on you!

 

Upgrade those lines while you're at it.