You can get by w/o the fuel mods, but spending the extra cash on larger fuel pump/injectors/etc. will prevent the engine from leaning out at high rpms and possibly causing problems in the future.
As a sidenote: I've got the older-style TRD supercharger on mine (with the grey housing) -- no fuel upgrades -- and haven't had any malfunctions and the truck runs like a champ. The only time it's 'pinged' is when it was accidentally filled with Regular 87-octane fuel once...
However, the older blowers, like mine, came with an FMU (Fuel Management Unit) that SUPPOSEDLY helped prevent that leaning out. But this wasn't widely confirmed, and the part wasn't included on newer units.
Just some info thrown your way! <img src="/forums/images/graemlins/kewl.gif" alt="" />