Well, JPJ used to allow 30% on Proton car before the no 'kereta potong' rule. Now requirement drop to 25% and strictly no 2.0 engine for any Proton except Waja Chancellor and Perdana but I managed to get my old Waja 4G18 swapped with 4G63T and endorsed back in 2005. That is why I still keep the car back in hometown for sentimental value.
If am not mistaken, Few Toyota, Nissan and Beemer doesn't require an alteration to original mounting. A mere changes in mounting rubber will do. That is why Beemer or Toyota with stock 2.0 can get 1JZ endorsed without any problem. Provided that brake and suspension is upgraded to cope with extra power.
Btw, I know a few 'people in authority' running on Waja 4G63T and others with upgrade exceed 25% converted quite recent but this is Malaysia, so, their have their way...
I used to send friends and relatives to LCCT in a heavily tinted stock black Perdana without any problem. Most recent is last december.
I got away from the roadblock with only 5 words..., they never ask further but even if they do so, I've got the answer!