One time I got down to 950 PSI with my Flex.. Saw Lambda also jump a couple tenths to .84. That's when I installed a KB Boost-a-pump. With Torrie's revised tunes and the BAP, I have never been below 1,250, and found the one which produced the most HP, kept FRP above 1,400. My issues always occurred in 2nd gear at above 5,000 RPM, and were most severe just before shifting into 3rd. Even at peak RPM in 3rd it had recovered nicely, and in 4th at the traps, my FRP was fine.