Yes turbos do increase power.....BUT the M3 motor does not lend itself to boost in stock form...the compression ratio is just too high to add boost too without race gas (even with it really)...so you will need to change the pistons to something lower to really get some silly HP out of one...BUT if that was done.....800hp would be easy...
2008 E92 M3, MR, DCT, extended BB leather, loaded!
1988 Porsche 928S4, Guards red/Champagne leather
1989 Porsche 928S4 track beast!!!