I have a 205 XRDT which has given trouble-free service for years.
Recently it started to lose power intermittently - it's just as though I
took my foot off the accelerator, so it just ticks over. Then after a
minute or so it's back to normal. Full power is available when required,
unless there's none at all. I can feel the turbo coming in as usual.
    It might be ok for several days, or happen several times in ten
minutes; either cold or hot. It always starts first time, even after
standing for a couple of days, so it does not appear to be air leaking
into the fuel line. No drips on the garage floor/on the engine, so it's
not fuel leaking out. I can't find any particular circumstances when it
happens - going uphill/downhill/round corners whatever.

I have:
1. Drained the filter bowl & blown out the fuel feed & return lines - no
problems.
2. The manual primer pump on the filter works ok.
3. There is no perceptible hiss on opening the fuel filler to indicate a
blocked vent to the tank, and while blowing out the fuel line I can hear
a hiss from the vent.
4. It has been relatively warm recently, so it's not going waxy.
5. Checked connections to the solenoid valve.

Any ideas, anyone? I'm stumped.

Dave