Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
is there any point in strappin a turbo to a 4cyl vectra?
Na your explanation was about 90% wrong. The wastegate has nothing to do with the blow off valve, the air leaves the turbo before it goes through the intercooler if the car has one and the turbine spins on the exhaust gasses which spins the compressor wheel. The compressor wheel sucks the air in and compresses it before sending it to the intercooler.
Did you read the link i posted earlier?