VAFC's do bend the ouput voltage of the ECU, which imminently after the tune is great, although the changeable points is very very limited, and only adjusts full throttle, but the ecu will learn and over write all the VAFC fuel settings due to the long term and even short term fuel trims.
Which results in the car's with VAFC's requiring another dyno sessions, there's only so much piggy back devices can do.

I find a lot of people spend a little bit of money on pointless modifications, rather than saving a little and getting the best....the amount of untuned vafc's running around out there is crazy ! purely because of the fact the ecu will auto learn.

A typical stainless steel exhaust system with a nice mulfer costs around 1500$ + add on the cost of extractors and that’s upwards $3000. Now I can guarantee you will get more HP increase from tuning a stock car with a fully tuneable ECU than you will from bolt on modifications such as a new exhaust with extractors for much less than the cost of a ECU, iv done the tests and proved this many times the stock exhaust is not “THAT” bad anything can be improved upon tuning is where all the power is.

Regards James