Painting your leather seats even with leather dye is just asking for it... You'll wreck the seats and then have to get new seats or have them done custom in black leather which is the way to do it anyway. The only real professional way to do a black interior would be to gut the interior, do the trim/dash correctly, have the seats recovered and do custom black carpet/headliner too. Completely not worth it IMHO. If you want a sporty sedan with a nice black interior, sell your CSVT and pick up a late 90s BMW 328i.