Replace fluids and filters if you don't have reliable records. Torque converter has a drain making it a simple task. Read up on the filling procedure after you drain the TC if you're not familiar with these ZF ATs. There's a filter at the bottom of the power steering fluid reservoir.

Don't mess with the transmission vacuum modulator until the rest of the vacuum system is tight.

You replaced the air cleaner or just the air filter? Check the rubber pads holding the air cleaner above the manifolds. It gets noisy when the rubber pads break.

Sixto
87 300D