I am scrapping one next week with a almost new down/flexi pipe.

The tinny sound is normal silencer baffle degradation, your exhaust is 8 years old I presume ? the burble on overrun is a air leak in the exhaust , probably a split in the flexi hose beneath the silver mesh. The "white smoke" looks like condensate. Not Smoke . vapour is not smoke . Hypocho...

Last time I had the white smoke it turned out to be a turbocharger spindle with too much play (end float) on the spindle , which leaked oil past the seal onto the red hot impeller which resulted in a a huge cloud of white/grey smoke . occasionally. Take the inlet hose of the turbo , grab the spindle...