The car: 1997 Turbo 2000. Moderate performance upgrades: VF28 turbo, Link version 1 ECU, uprated fuel pump, larger injectors (not sure what size), STI intercooler, decat exhaust all the way through. It is running 1 bar of boost. All mods were done before I bought the car (around 9 years ago) so I don't know the level of tune, but I'm guessing it is similar to STI spec for that era (280 to 300BHP), i.e. nothing crazy.

The problem: I have recently noticed that it is blowing big clouds of black smoke when driving on boost. I replaced the adjustable fuel pressure regulator earlier this year (was leaking) with a different model. I adjusted the pressure to approximately the same as the old one, which was 3.1 bar with the vacuum hose on. To be honest, I don't know if the smoke started immediately after this change, or whether I have only just noticed it (quite possible as I hardly ever take it out of the 30MPH zone these days). A few months ago I managed to flood the engine after starting the car from cold briefly to move it, then stopping. It took several 1 minute sessions of cold cranking with the crank sensor removed to get the excess fuel out of the cylinders the next day before it would start again!

When driving around off boost or very minor boost (2 or 3 PSI) I see no smoke out of my rearview mirror.

My questions are:

- Is this likely to be an over fueling issue? Or something more serious?
- For a car in this level of tune, what is the approximate fuel pressure I should be running? I have read that for a standard car, it should be 3.1 bar above manifold pressure. If this is the case, mine is over by about 1 bar (3.1 bar at idle with vacuum hose connected to FPR, which would be around 4 bar above manifold pressure).
- Could it be caused by a bad MAF sensor? If the MAF is stuffed, will the Link ECU over fuel the cylinders to be safe and avoid detonation?

Any advice much appreciated.