Light vibration Venture '99 steerwheel

The following problem ....

My Venture from ' 99 is in very good condition and does it perfectly. 198,000 KM fresh head and intake gasket blabla just a good truck.

Last week I drove in another Venture (bought for parts/destructor) and it struck me that this car was directly on a lot quieter.
In that sense I felt much less roll sound of the tires and very slight vibration in mn steerwheel ....

After this ride I am heavy obsessed (hahaha) why my car is not so quiet ..... without the test drive in that other car I had this of course never knew ...

the facts:
Yesterday car on the garagebridge had and everything is pretty good condition....no play on the bearings or so.
brakes are new (disks blocks) and turn freely.
The Steering knockels are both new ..... .
The 4 tires are of Continental Exellence (expensive tyres) and also 2500KM under my truck.
The tyres pressure is 2.5 Bar all around.
Changed 4 of the other tyres from the Venture also makes no difference ( Meteor tyres ) . ...
no details bearings/or drive shafts.
Let it run on blocks in D and no strange things.

With driving on a road feel just very light a rolling vibration by the steeringwheel and carbody ... not serious but present.
I'm going on a bit of rumbly or rough surfaceroad I feel it much more ... but that have all cars ... ... ..?

What i found. ...

With accelaration the vibration is as good as gone .. ... ... Let my feet of the gas is there again .
Right or left steering does not matter worse or less.... brakes either.

It is there at all speeds ... .... so from 10 km \ you .... on Highway is also not worse or something .....

When accelerate in neutral it gives NO vibration in my steeringwheel, . so motor/trannymounts can I also can exclude.
Let out roll in neutral the car gives still slight vibration ... ... ... ... ....

I think its the top strut rubbers or something... .... ?

Anybody an idea? (sorry for the bad English.... haha)