In relation to the Air fuel ratios, it doesn't matter which boost controller you use to make extra boost, your mixtures are completely reliant on the tune in the computer. You can run 12psi on an electronic boost controller or manual bleed valve and the mixtures will be the same. They say the manual bleed valves are no good because they release "metered" air but it's a negligible amount. Don't let that issue sway your decision.

You can build your own manual bleed valve as outlined earlier and you can minimise the amount of air it releases by using a tight restricter as close as possible to the wastegate actuator and have the bleeder jet after that.