Neil Dickinsin

You will need to get it scanned and find the fault code, this will point to what the issue maybe but will need investigation and confirmation.

http://wiki.ross-tech.com/wiki/index.php/Diesel_Particle_Filter_Emergency_Regeneration

I fitted a k&n (as this will be less restrictive than a standard filter) to mine and also retro fitted the sock that comes with the standard filter(the sock washes out with detergent). I would also keep the standard airbox as this in my opinion is better than an induction kit as it keeps the hot engine air completely away from the intake.

You should have a label on the drivers door showing tyre/wheel options and tyres, normally if you increase rim size and keep width you would need to reduce wall height also have you checked offset.

Yes

Mr muscle oven cleaner and T cut.

Don't forget MOT's have been changed last year for diesel emissions i.e. no visible smoke, so I hope you have a very good remap? https://www.gov.uk/government/news/mot-changes-20-may-2018

Try https://en.m.wikipedia.org/wiki/ZF_8HP_transmission

Or try Rps online

Try Wikipedia as a starting point as this list information on different engines and gearbox combos. You need to decide if you want low tax or BHP then what your budget is. BITD 313 - 326 PS 650 to 700+Nm. These have tiptronic 8speed transmission. Tunable to around 400bhp.

The should be J code and some other digits stamp on the inside if the rim.

M+S are winter tyres, I would fit the 215/55/16 the 55 means the tyre wall height in % of width. So running 205 tyres will give you a slightly smaller overall diameter so will show less mpg.

Just watched video and looks like water vapour of a cold exhaust on a cold day. Monitor coolant and oil level and if no change proberly worrying over nothing. Have you checked oil is not over filled?

Try 7zap.com

I have just gone old school and fitted the old yellow stoplock that fits throght the steering wheel, also not leaving key in front door anymore as I have seen they blow torch upvc doors and put hand through to get key to brake into house to steal car keys.