After tinkering with an intermittant fuel delivery problem for some time, change of the fuel pump relay now made my car run stabil again. But after this period, it seems like it havnt got quite the power it used to have. It is an automatic and it also runs longer up in gears as before. Turbo Pressure seems like a little lower. The spark plugs look whiteish, I remember them like a little light brown before. What can cause it to have leaner mixture ?? Never misses a beat, and starts just fine. Can the katalysator have melted a bit down ?? It has 230000 miles on it. No oil consumption, maybe 1/2 l between changes. Have used Mobil 1 even since 125000 miles, stopped the small consumption that had appeared then. Any guesses. How do i get the power back.

 

This is just a guess, but if you solve your fuel problem you will solve your power problem. If the plugs indicate a very lean condition, you aren't getting power because your not getting fuel. If your turbo was working recently it probably isn't a problem now. What does your boost guage read at full throttle under load? If it indicates full boost your turbo and waste gate are probably OK.
Focus on fuel delivery.

 

Thanks for your reply, appreciate any help.

Now those stock gauges arnt state of the art, but it reads close what it
ever did. Somewhere between neutral and full boost, like a third of the scale between neutral and full, at most

They never reach full boost. Turbo functions and rotates at least. It has a week rattling when cold, started lately. I was wondering if the lean mixture can have harmed the turbo. Can a turbo be weak or is it just working or non working. Are there any components in fuel system that can cause a lean micture and still be stable ??