Larger tires always extract a heavy price from performance not only due to their added weight but moreover due to the up-gearing of the driveline. NMKawie wasn't kidding when he said, "Besides, that 800 just won't have enough "puppies" to turn the 32s let alone the 40s in high range without taking a week to get to ..40mph".

It must be a dawg now.
Now how to get some performance back. (You won't get it all back. 32 inch tires are a huge jump)
The Power Commander won't do anything by itself. Your EFI system is quite efficiently mapped and optimized for the stock cam timing, intake specs and exhaust specs from the maker. Maybe richening the mix in some areas will gain a speck of oomph, but hardly enough to matter. If you slap on more performance enhancing doodads like a cam or a radical obnoxiously loud pipe a PC can optimize for those things and then you gain a bit, at the cost of annoying everyone else.
Clutch reclocking as described on this site will gain you the most you can get but still I don't think there's anything practical you can do to completely reverse the upgearing penalties of 5" taller tires.
Keep us up to speed on how it's going though. Thanks