If it's chucking out quite a bit of black smoke, don't just assume it's the pump. (If you have)
It may have been tweaked, but there may be other factors which are making it smoke. First rule out that the engine is getting enough air to match the increased fuelling. Check the air filter isn't dirty and old, and make sure that there are no splits in the induction pipework. Is the intercooler in good order, and if there's a snorkel fitted, is it fitted correctly and as non-restrictive as possible.
Also consider whether the turbocharger is supplying enough air for the tweaked fuelling. Instead of cutting back the fuelling, you could tweak the turbo to match (if it hasn't been already) as there's scope for a healthy turbo to boost a little more. This way you keep the benefits of the improved power with less particulate slag being deposited out the back, although a tuned TDI will generally always smoke a little more than standard.
If a TDI is tuned with both the fuel pump and the boost pressure accordingly and in moderation, you should see minimal more smoke (as bit is inevitable, especially off boost) increased power, and no real negligible effect on fuel economy.
Worth a thought.