whats efi ??
prob best idea to take the parts to mitsi themselves. just tell (ask nicely) the garage for the parts to see if mitsi can find the problem that way your likly to get some informed feedback.
if its welded on them something must have been rubbing it takes alot of heat to weld metal. so i personally think you would have felt something and if youve ever smelt the air when theres welding going on it goes right for your throat