gear box modulator

[sic 40t]

hi i have a 85 kb lazer about to get it rego. If you leave it running 10-15 min then rev it it blows smoke i thought it was valve stem seals put a brick on the gas pedal and rev it 3000rpm for a one hour all good now. Left it for a whole day then started it sweet but no gear box oil no leaks they told me it the modulater on the gear box sucking the oil into manifold and burning it sound right?. What does a modulator do???????