The Veco 19 are great engines. They are from a time when mufflers were not used and fuel draw was relying on suction only, so there is no need for muffler pressure. For the later models with increasing sound regulations, a muffler is available but there is still no need for muffler pressure.

The engine should spin a 9x4 happily around 12500 rpm (with stock muffler), make sure to use only full castor (20-25%) and low nitro <10%. It will pull a trainer style plane of around 1.2-1.4kg in weight without any problem.