Is the turbo still std internal wastegate? If you have improved both intake and exhaust flow, are you sure it isn't spiking because the wastegate just can't pass the increased exhaust flow?

After full exhaust and intake mods mine would start to spike from 18psi til it hit the overboost cut-out, it just couldn't pass the excess exhaust gas through the wastegate and so it went past the turbine and created more boost, therefore more exhaust gas, vicious circle!
Ended up pulling the turbo off and porting the wastegate for high flow a couple of mm and all sorted! Would hit the set boost level and stay there solid as, no more spiking..

just did some research on these things, there is no reason to buy an expensive one!

if you dont want full feature which im guessing no one is really using?

you could make the same with a hobbs pressure switch and a solenoid very easy, it would not be as easy to adjust, but adjusting your boost is gonna throw your tune anyway, should be setting boost once during tune and leaving it well alone

anyway, being such a simple device i cant imagine why a cheap knock off would realistically be any worse off than a brand name job (thats more than likely made in china too)

this looks good with built in gauge!

ebay link

if you wanna DIY buy these two

Hobbs-pressure-switch

solenoid

but your almost up to the cost of the kit with gauge and easier adjustment knob 9hobb switch requires turning with allen key

i used an identical system to feed my carby high fuel pressure after boost went over 3psi on my carby turbo setup years ago

lol had to laugh today, just discovered two 12V solenoids on some hydraulics at work that are supposed to be 240V, getting replaced tomoz... old ones will be going in the bin...but might not make it that far

best to recycle as those electircs can cause havoc with the groundwater in the tip.....