Have box fitted to mine. Had no problems what so ever with it. Pulls very well indeed. No clouds of black smoke or boost problems. I would double check you have it connected correctly. as far as i know the amount of boost is controlled by the wastegate, so if yours is overboosting maybe your wastegate is not opening correctly/sticking but you only notice it with the box on. Worth a look if nothing else
Did mine during the week. Was surprised how clean it was,just a light misting of oil. Had a bmw 325 tds (same engine) that had a layer of hard crud about 5mm think all around the inlet runners. I've had the egr blanked for a while which helps alot. I also found the manifold gaskets were missing due to a previous numpty owner. Does make a difference after a good clean out.
Thats good news, after finding the gaskets missing had visions of previous owner doing a vanishing act on the sensor. All done now anyway, no more oil mist blowing out of number 1.
Decided to tackle the blowing inlet manifold tonight. On closer inspection it looked like a previous owner had been there before. One manifold bracket missing,the other only had one bolt in it. Once the manifold was off, all 6 gaskets were missing. Manifold was pretty clean inside just a slight misting of oil. One thing I noticed was a bolt where the Air temp sensor should be in the bottom of the manifold, should a 96 td have one ? . I can't find any spare plugs/cables for one.
Box came from a company in germany MAL electonics, Just connects to 4 cables in the main ecu plug. Fully adjustable from normal power to 30% power increase. http://www.mal-electronics.com/html/englisch.html
It's listed as td powerbox, only took 2 days to arrive from germany aswell.