Like Luke said, the MAF will measure this increase/decrease in airflow & the ecu will compensate for this. Now your tune may not be dead on but I've run from around 12 psi to 20 or so psi all on the same tune (when was running Greddy Profec Type S EBC) & there wasn't enough difference in the tune for me to notice anything in perticular. Your air/fuel ratio may change like a couple tenths or something, but were not talking anything major like say going from 11 to 1, to 10 to 1..
The best solution would be to get that LSD on your wish list & make sure to run a nice sticky set of tires, they you won't have to worry about running different levels of boost
