Yeah. If the manifold is cracked, get that fixed before you go too much further. No sense in trying to diagnose any other issues if you know that’s broken. Fix that, then see where you’re at. Your best bet is to replace the manifold with a good one, unless you know someone who can weld cast, or it’s an aftermarket, non-cast header. Post-turbo exhaust leaks are noisy. Pre-turbo ones cause running issues. Basically, everything from before your downpipe should be a sealed system. Starting from your MAFs, to the turbo inlet, to the intercooler piping, to the throttle body, to the manifold, out the head, through the other manifold and out your exhaust should be completely free of leaks, or you’ll have issues. All the air that passes through the MAF sensor needs to stay in the pool and be accounted for. If you loose any air after the MAF sensor and before the downpipe, you’ll have running issues.
Stock motor mounts shouldn’t matter, if they’re shot you’d notice them because the motor and tranny would be flopping around like crazy as you’re on and off power.