well i got a V6 gen2 and i've simply cut the bottom of the airbox out with the stock filter still in place plus a much smaller rear muffler and its a littler cleaner in the top end, say above 5000rpm but apart from that it hasnt done anything as for auto vs manual lets just say i wish mine was manual, mine is a slug in 1st and the shifts are way to smooth and slow even with the POWER button on