Not the sort of experience anybody might expect to have with any company making it's living that way. I hope everything is resolved amicably in the end.
I wouldn't be too worried about welds on the dpf, I personally feel that visual checks on the dpf ar e along way off yet. Alrhough listening to some rumour mills there are plenty of people who swear that they're first cousins ex-pertner's best man at the wedding, who works for VOSA, said it is coming in tomorrow.
Either way, bear in mind that the MOT smoke test is still very generous, considering that cars like old Peugeot 106's running on vegetable oil still pass the test, despite making plenty of smoke. The test carried out is as below...
The engine will be accelerated up to governed
speed and the smoke density measured.
Engines that emit very little smoke and achieve
a meter reading of 1.5m-1 or less will pass the
test after the first acceleration. However, if the
test is not passed on the first acceleration a
further two accelerations will be carried out.
The average of the three acceleration readings
will be calculated and if the reading is at or
below 2.5m-1 for non-turbocharged engines
or 3.0m-1 for turbocharged engines, the
vehicle will pass this element of the test.
However, if the average is higher, a further
acceleration will be carried out, and the average
of the last three readings will be calculated. This
will continue up to a maximum of six
accelerations. If the average of the fourth, fifth
and sixth accelerations is higher than the
appropriate level, the vehicle will not pass the
In addition, vehicles may be refused a
certificate if the exhaust emits excessive smoke
or vapour, to an extent likely to obscure vision.
So if the smoke at governed speed (engine on the rev limiter) is slight, then yoiu will most likely pass the test on the first run. From what I've seen a lot of tuners don't play around with maps at the governed speed and let the engine run into starvation, there's much more torque to be had at lower revs, so the smoke produce at the governed speed might be no worse than a standard car.
The lack of a dpf is nothing to worry about, even if it's smnoking badly under hard acceleration (when running at stoichiometric optimum it should smoke), mine has just passed the MOT on the first run with a 2" hole through the dpf.
I'ld be surprised if all of this hasn't been explained to you already ?
Yours is the sort of story I read before I was prompted to see what changes I could make for myself before I had to start paying people who make money from doing it. It's only cost me some time and about £15 in hardware, and I have a blanked EGR and a dpf which is drilled through, and regens don't take place. Pretty hassle free, thankfully