[1795]

Where is/are your pickup(s) in the fuel tank/cell? How much fuel are you running? In a hard corner with a moderate to low level of fuel you could be sloshing the fuel to one side and briefly sucking air into the pickup and that could be contributing to the lean mixture on cornering.

The rear-end sliding out could be secondary to brake bias, or you might need just a little more weight in the rear. Just a couple of thoughts.