MY FMIC kit currently uses a Vac block to control the BOV i'm including in the kit, because the solenoid cannot pull enough vacuum to properly open the valve I'm using at low, part throttle.
I was not aware this was called the "boost hack". During all my FMIC time and datalogs, boost curve, boost amount and boost spool time changed very very little, nothing I can notice from comparing logs. I didn't see a single psi increase from hooking up the valve that way.
Word on the street is the ECU is programmed to use the solenoid to bleed boost in a severe boost spike situation.
I have yet to find real, solid proof of the theory (datalogs, official word from kia/hyundai, screenshots from tuning program, etc) and I am going to do some digging to get a firm answer on whether or not this function is in the ECU.
If it is, then I will have to find a valve with a softer spring to include, or get springs right to use the valve I want to include with the kit. We will use the solenoid.
If it doesn't, then the FMIC will include the original valve I want to put in the kit, and a vacuum block to accompany it. The solenoid will be bypassed.
To conclude, running my aftermarket BOV straight from the vacuum block:
- boost amounts didn't change (spikes, holding, onset)
- no CEL for "mechanical valve fault" or whatever the code says. I would get this CEL if i ran my aftermarket BOV with the solenoid, because the solenoid wasn't opening the valve during light driving
- the vacuum block hook up would open the valve at all throttle levels. This would be very light thru my neighborhood and all the different times thru WOT. The valve opened lightning quick too.
Stay tuned on what I can find out about the solenoid.