Power loss, it feels like the turbo is not functional at all, uphill it simply does not pull at all, however I do hear some turbo whisteling now and then like when I'm go on high rev then clutch in.

Runs fine on idle

starts easily

fuel consumptions is not dramatically changed just slightly higher

no smoke as far as I can see from the rear view mirror

no "check engine" light.

Did not do diagnostic yet, it is rather expensive on local garage. No problem with engine before, noticed some gradual power loss the past 6 months, but now it is dramatically worse.

Did some trobleshooting, checked wastegate pull rod, moves fine with hand power.

Checked vacuum hoses, many in bad condition, but could not detect any holes or leaks. Removed one by one, noticed that there is no vacuum in any of them... ?? Where is vacuum produced... ??

Dismantled EGR Valve and cleaned (it was heavily gunged up), checked for movement of valve with pushing actuator by "hand" from exhaust side. It is spring loaded shut by default, iow no opening to exhaust in non operated posittion.

Removed MAF and cleaned with electronic cleaner spray. Newly changed air filter insert.

Removed vacuum pump for brake system because of oil leak, cleaned engine side, cleaned and checked mating surfaces and re-attached pump. My conclusion is that vacuum pump for brake system is not used to produce vacum to exhaust system, so I'll leave it alone for now.

Disconected black&white non-return valve in vacuum lines, I could blow through it from both sides, brown dust came out. Is it broken ?

My questions are simple: what should i check first ?

Want to check SAI tomorrow from underneith the car, how does it look like and how can i check it ?

Where is vacum produced; where is the source ? Should there always be vacum, also on cold engine and idle speed ?

Forgot to mention, Skoda octavia, 2002, 1.9 tdi 66kw

Problem solved.

My conclusions were all wrong, the vacuum is produced in the vacuum pump for brake system.

Problem was that the tiny vacuum suction tube was gunged up with brownish dust, similar to what was blown out of the black&white NRV in the vacuum lines. Picture shows after cleaning.

Turbo is now functioning as normal, but I guess I'd better take a close look at that NRV again, perhaps it needs to be renewed.