reads like a crap re-map from a crap garage pal , go get your money back and use one of the guys suggested
Have the say the man sounds right.
Its a basic cheap remap trick / technique for diesels to grab some more power is just ramp up the fuel pressure in the rail and inject more derv which makes the car run richer and causes more black smoke.
If your DPF has been hollowed and your EGR blanked off you're going to get more soot out of your exhaust anyway as this isn't being recirculated or captured by the DPF (how do you think it clogged in the first place....).
You may want to conclude that this is 'normal' [give work done to your vehicle] and carry on. Thankfully they only measure what gases come out of your exhaust, not the amount of soot that goes with it, so it will pass and MOT.
If you're seeing black smoke all the time, and not just when you boot it, you may want to look further.
As a basic rule every engine is as unique as a finger print, they all run very slightly different, use slightly different amounts of fuel produce slightly different amounts of gases etc and this is compounded by the engine's service history, use, treatment throughout its life, where you live, everything.
Therefore when a car is remapped a good mapper will have the car on a roller, tune the map to suit the car and the drivers requirements and re-roller it. Possibly followed by a road test and whatever tweaking is required and repeat until satisfied.
If your remapper plugs a box into your car, waits 15 mins and sends you on your way they've just flashed a very basic map to your car and not really tweaked it to your vehicle, so you will often find power gains are not always as great as claimed and can come with some interesting side effects from time to time - a typical one being shed loads of smoke. You could (but I definitely don't want to start a debate on) discuss accuracy of rollers etc but they still measure exhaust on a roller and you'll get a before and after figure so you at least know what sort of gains you're seeing.