Injector Question.

[ajh]

Not having a lot of diesels over here I don't have as much practical experience as I would like and have a couple questions that hopefully someone here can answer. I'm looking at lot of things at once so I might be a slightly confused.

My assumption is that when tuning and turning up the fuel delivery, the point when EGT skyrockets is generally caused by unburned fuel burning in the turbo/exhaust on the way out (my probe is in the turbo downpipe so this probably shows this state quite well). Is this possibly because the injection duration exceeds the burn-time window due to flow volume and an indication of faulty or possibly that larger injectors capable of increased flow in a shorter timeframe would be a reasonable option? I don't think my injectors have ever been replaced and the engine had about 350,000mi on it (200TDI) before I got it and I'm trying to tune for power. I can get things stable but I don't feel that I'm getting as much power as I should be and the fuel economy is pretty poor (seems to be about 20mpg). There is no visible smoke until the throttle is wide open and then it's just a light haze. I do get a fair bit of soot on start-up but in a single puff unless things are cold in which case I get black smoke for the first few gear shifts and then it's fine.

I keep coming back to either injector issues (leaking?), FIP issues, or excessive ring-wear, I haven't been able to do a leak-down test yet (I'm on the road) but I haven't seen much on here dealing with the effects of injector changes and cut-off pressures, flow rates, etc and would love to learn more so I can properly diagnose what's going on. I've tried to read as much as I can but there's still enough missing experience to properly diagnose things, I seem to have pump tuning down pretty well though