you'll always spike.. it's hard to get no spike at all. I'm set at 14-15 psi but i'll spike up to 16 or 17. it all depends..and i dont get what this 'bar' stuff is. heh. i just have a regular autometer ultra-lite boost gauge that measures -30 vacuum up to +30 psi of boost. but getting a catback N1 should be fine.