Just been advised to add some cleaner by local indepandant.
Revved my tdi up and left a big black patch on the wet road.
He went round the back and put his finger in it and it was at least 2-3mm thick.
He asked how long it had been smoking - told him since i bought it 2 weeks ago.
He asked does it accelerate smoothly or have sort of flat spots through the rev range - told him it accelerates and then 'hits a wall' while revving up
Told me that is what happens when tdi's are used on short journeys all the time.
I told him I used STP Pre MOT and he chuckled and told me it's like adding a thimble full of water compared to the stuff he uses.
Got a bottle of Forte off the shelf and charged me £16 for it and told me to blast it in 3rd down a dual carriageway at night as it upsets less people.
Chucked it in and took it for a short blast at 60mph in 3rd. I hate revving engines past half the red line mark (eg red line 6000rpm- m limit 3000rpm) but he told me it's got a big timing belt on it and not to worry.
Seems better already and a bit more responsive.
Definately less black smoke.