youll be venting air that is supposed to be metered by the maf and there will not be any compensation afr wise everytime it vents due to the maf not being able to register the lost unmetered air.

vented bov should be on speed density.. anything else is not correct.

 

I have a friend that came from NY with his Evo and he was running VTA with his HKS SSQV and NEVER had an issue until he upgraded his turbo....now the car runs like crap. I personally didn't think it would be possible to run VTA unless on SD or standalone but his car proves me wrong.

 

most likely his other turbo was only opening the smaller valve and now his bigger turbo is opening both valves during cruise and causing issues. ssqv is a pull style valve design with 2 valves. once enough pressure is reached the smaller valve opens, then the bigger as well once pressure is met to open that valve as well.

ive ran vta back in 2003 with greddy type-s when it was popular and had little ill effects on gutted maf.. you can tune around the effects, but its not correct. the only way its correct is with speed density.

you can get away with it tho on some bov's.. the synapse bov is one of them im pretty sure.