First, let me say that I am no expert by any means, but I must ask the question.

Have you considered using a bladder tank?? I am putting together a P7 and have considered this. For some reason I think it will work.

FWIW, 2 guys from Texas came up for a CPA meet, both had P7's With OS55 engines (1 with the Evo performance muffler, the other with a Jett). Both had engines leaning out/deadsticking during the outside loop maneuver. One of the local guys (with a OS .61/Jett) mentioned he had the same problem. He advised them to open the muffler nipple one size (turn drill bit with hand). While it did not completely cure the problem (they still experienced some hesitation), it did stop the deadsticks and both were able to compete both days.

Just a thought...