GL1500 hesitation when accelerating, all gears

Hi,

I do have off-idle hesitation problem, but also hesitation in higher speeds. Actually, when ever I try to accelerate fast, there's a little time before anything happens and there is noticeable hesitation.
But, if I accelerate heavy, 1st of 2nd gear and continue accelerating through gears (to high rev) there's no hesitation. And I think, that I have mileage ok and after all as much power as there should be.

I read a post about vacuum error, not leak but there is a hose that goes "stuck", I mean that there is actually loss of vacuum. Just can't find it now.

If I release throttle a bit, hesitation isn't that noticeable.

I clear this out more, if I try to overtake a car, I'll have to throttle very gently at beginning, wait a while when the acceleration begins and then twist more.

Suggestions where to begin? Is it very hard to replace all vacuum lines?

Bike is -88 and has now 200k kilometeris in it, so I'm wondering if to leave like it is and ride peacefully, or try to fix this.