For the price difference between a B18C1 and a B18C5, you could do a lot of mods that would bmake the C1 outperform the C5. IMO the C5 is a sweet engine, but not worth the additional cost. Also, the C1 and the C5 aren't the most turbo-friendly engines. They CAN be boosted ( I am) but you have a small margin of error so-to-speak because the compression is so high.