I see you are more of a mars bar half eaten guy than a mars bar half uneaten guy. I prefer to view life with the attitude that my mars bar is still half uneaten.
The air intake pipe is buckling under duress of the increased air flow which is causing the reinforcing wire to rub against the alternator when it moves. Just a guess!
Yup, I did this! Transit seats fit perfectly in the tub of a 90 and as the have built in belts, you can put kiddy seats on em too. Gotta bolt em through the floor and yer advised to brace em too.