The question is a bit odd as no venturi's are available for this engine. The stock venturi works just fine on suction. If your looking to choke it down, that might be slightly tricky. Paul Smith had a great tutorial on how he does it on TD .049's using JB weld. You can't block the peripheral holes internally. Paul would use small pieces of wire and fill the venturi with JB weld. The TD .09 while it may be used on crank pressure, it's needle valve is quite coarse and really wasn't designed for bladder pressure. As long as you have no air leaks on the POS plastic carb body and needle valve, it works fine on suction.