are you going out sideways or up ?
The
genturi will do the job going UP because heat rises,
but if you are going sideways, then you need to seal the exhaust so it will flow out...
Here is an example of some flexible tubing you could use
you will need a metal (non flammable) adapter between the 1.5" or so genny exhaust to the 2" tubing, etc...
when we used to do dyno testing with the tuned engines, we would just attach a large tube to the exhaust and direct it outside...
good luck