wfhan,
i've also heard from many car owners, esp same engine capacity and same makes (means proton to proton, or toyota to toyota) do not require kawal selia due to no increase in displacement at all, however i didn't go through this route so i disclaim my advice from any legal suits, u still gotta ask around, also i tried many times asking different JPJ branches via phone calls or personal visits, each will tell different story, please be careful....
all i'm saying is that branches have limited rights to approve certain applications, but putrajaya as the HQ will have all rights under the roof, eg. my left hand pillar change, i was surprised to see certain repair apps (after accident) needed to be reported and request to be made to JPJ for notification and approvals, and the branch has a list of what are the things they can approve and what can't which will need to go through HQ, that's what we call escalation!!
happy motoring...