Hello, iam from the Netherlands and i have trouble with an buick v6 3.8l engine. The engine strats great but you can hear an misfire. when you give more ga he wil back fire out of the carburator. this problem is not related to one cilinder.

I hope some one gots the answer.

 

It sounds like the spark is getting to the cylinder too early and firing the mixture too soon.`
That could involve the position of the distributor as far as timing is concerned.
Another thing could be spark plug wires and how they are placed and routed.
How about you tell us everything from the time it first started and what you did if anything?
Can you see any carbon tracks inside the distributor cap ?
When were the plugs and timing last serviced?
If the carburetor accelerator pump is not working correctly the engine will not respond as it should.