18psi on stock sleeves? that's pretty good. what compression? what kinda power you making with that setup? i'm in the middle of building something similar...built head and internals, stock sleeves, 10:1 compression (9.5:1 at the lowest)...but i only wanna make about 300whp or so. i don't plan to run that much boost...

you should probably sleeve for peace of mind if you wanna run more boost, cuz 18psi is getting towards the limits of reliability on a daily driver, i think...