My old Bug Eye used to have what I can only describe as a hand brake cable twanging sound when backing off but closer to the door behind me, after much searching, tightening & someone hanging their head out the open back door it turned out to be the Bosch fuel pump.

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Beaten up old 98 Gen 2 Liberty, 13.0, stock V3 STI running gear.
07 Transit motor home
69 VF & 70 VG Valiants needing full restoration
Yamaha Zooma 50cc rocket hopefully going with the Transit.

i have the same issue when backing off the throttle.. bugs the hell outta me.

Hey I had the exact same rattle noise, my mechanic found the heatshield on my downpipe had cracked, he fixed it somehow, not sure tho, was only a $30 fix.

Watch this video to see if it is the same noise

Subaru wrx rattle noise on throttle release - YouTube

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WRX Club Spec Evo 4