Jd@af and hxman i think he said the "most" hes ever heard of any si running was 23 psi . And i agree with JD@af about going with turbo charging it . Power !!!!!!!! cha cha cha Power cha cha cha Power !!!!!!!! cha cha cha ......V-8 killer cha cha cha V-8 killer cha cha cha .....Rustang killer cha cha cha hehehehe