[UPDATE] SOLVED! Hurray!
The muffler had corroded inside and it blocked the exhaust system, making bad to motor. I got it fixed and the car energy efficiency improved from 12-15 liters/100km to about 6-8 liters/100km, remarkable cost saving! Wow! Thanks to all answerers! It cost about 200-300EUR for the part/installation in Järvinen/Hervanta. It is also possible to do it yourself, you need to see the bottom well otherwise just wasting your time -- car mechanic pretty much improvised when there was some little leakage in exhaust adding there blocking material "kitti" (necessary to get car through "katsastus").
Old Volvo GL 440 and this is coming out of the exhaust pipe. No noise, all working fine but this cosmetic thing: does it mean that the exhaust gases are now not well filtered out? Does this mean that the catalysator need to be replaced or something else?
Looks like Fiber-glass coming from resonator
Looks like stuff coming from muffler