...how much$$$? stock 1998 Audi A8 Quattro 4.2 V8 - AWD

That depends on what kind of supercharger you get and where you get it installed...It would definitly be around $2,500....no less than $1,500 for the supercharger alone....with everything, it would mosty likely be around $3,000 or upper 2k

You would need new gaskets, new headbolts, new compressor pulley, new camshaft, new intake tube, new injectors....the list goes on...I did a google search and couldnt find any specific sites that sold supercharger kits for the A8, but if you search on LLtek.com, Tap1.com, goapr.com, or any of the audi racing parts sites you can prob find one