its more than likely your boost controller. Manual BC tend to do that. Also alot of the XS bov i have come across leak liek no ones business, its those damn washers they use for adjustment. sole reason i now only use HKS SSQV and Blitz Bov. They are the only ones on the market that don't seem to leak consistently (by which i mean never leak, and is consistent about it). Whats are your a/f levels? How much timing are you running? Have you tried bumping up the octane, therefore you can run some more timing as well as run a leaner curve? I knwo fords o2 sensors don't like it too much, but it would be worth a try. 388 is not all the 57trim has got
I would love to see a 430+ whp contour...
