What tyre pressure were you running in the rear? Might be worth trying to drop a few pounds if you're really suffering from inlift. Bear in mind that if you use normal compressed air your pressure will increase by a few pound (depending on the weather). The harder the tyre the less it'll grip for you. I'm not saying it'll cure inlift totally because it won't but it might help to return drive sooner.
The other option is an obvious one but not a much fun, just don't get back on the throttle as quick, wait a fraction of a second later to go wide open and you might carry more speed from apex to exit back by not wasting time waving an inside wheel around
If all that fails then just weld the bastard! At the end of the day it'll be 10 times better than an open jobby and trackday cars should always be setup for a little understeer anyway
Have you got another day booked?