Start making similar adjustments to what you would do in the rain. I would start by narrowing the rear 5mm at a time. The goal is to get the rear outside tire to ‘dig’ into the track. Narrower rear track will help the kart tip and dig instead of sliding. If this helps you might find you need more front grip as well. This can be accomplished by widening the front track, adding a front torsion bar, or adding caster.
LV mags are meant to keep the tires in the operating window and keep the tire cooler. Most guys run aluminum wheels in the wet to add grip. And the LV wheels are almost no different feeling than the standard mags from my testing. Probably more of a marketing ploy than anything.
I wouldn’t mess with wheels here, there isn’t a lot to be gained. I’ve had success running MXCs on cold slippery tracks before, so wheel material isn’t a dealbreaker when it comes to cold track surfaces. Where it really becomes a valid tuning tool is when you’re trying to keep the tire cool in a high-grip, hot weather situation.
I’ll agree with the rest of Matt’s suggestions other than the higher tire pressures. Depending on what tire you’re running, a higher pressure can actually crown the contact patch and keep the tire from really digging into the track surface. We’ve found this especially true with the Bridgestone YLB/YLC tires. The MGs also seem to like lower pressures if you are looking for the kart to “dig”. There’s more to it than just trying to find “grip” out of the tires. You’re trying to get the kart to lift and take a “set” in the corner instead of skid across the surface.
What type of kart are you running? If it is a OTK Kart I was always told that you want to use a harder axle when you have to much grip and are trying to free up the rear. otherwise if it is something else then yes a harder axle usually applies. OTK Karts are usually the opposite of other karts but I did not know what kart your running