Changing exhaust wont impact insurance claim, the only thing which impact if you add additional racing bars, roll cage, change different engine (even same engine with different no. also cannot) without JPJ approval. Most insurance company in Malaysia wont insured heavily modified cars for racing purpose unless certain special insurance for official sport/track racing event.

Not necessary, if they detected your ride is heavily modify (not comply to original spec.) & different engine no. they can reject the claim on the spot. My previous mechanic got 1 customer after change engine, no go puspakom check & JPJ to register it's new engine no. and involved accident, the ride until now left to rot due to insurer no accept the claim due to different engine no.