being a mech at a Mitsubishi/Proton dealership, yes...they are pure Mitsubishi
Proton essentially bought the spare/2nd's off mitsubishi in order to cut costs when they were starting out........
You may find that Hyundai and Proton have some similarities too.....since that Hyundai also ran Mitsubishi running gear....and both hyundai and Proton are Korean
Incidently, the 2.6L TB is a bolt on upgrade to the GTi motor