Those are Grubee's current spec's and most follow those.I've said this before but I personally run at 185 psi and have setup peoples engines at the same with stock bearings and no issue.Folks whom inquire about porting are more likely looking beyond that of a commuter and trying to get all they can from it, alot of us are using scooter pipes that are 2 and 3 staged with very broad band widths compared to the dirt bike pipes and others.4k band widths can be had easily.Port area's and timings should match the other components used meaning that carb size and pipe length along with flange dia/header dia all have to work properly together when considering the porting needed.