Why is it(classic WRX) taking ages for the dump valve (VTA) to close back up when I back off the throttle, I have tried a couple of valves to rule out the problem if the valve was broke. I now have to run without out 1 and now and then blowing my intercooler pipes off lol.

 

Put the standard one back on.These cars are not meant to be run VTA as it screws up the MAF readings

 

It was running fine... could this be an ICV issue?

 

no its an ECU issue,the VTA is causing the MAF to send the wrong signals to the ecu.This is of course you have had the car mapped for the VTA dumpvalve in which case ignore the above

 

Yeh I got this mapped hks ssqv on my apexi fc. I now have a different valve but i did have issues before i took the hks off?

 

in that case it could be a MAF issue

 

which dv do u have fitted now?

 

I have a diaphram type, not sure on make.
MAF sensor hmmm not thought of this in the equation could be.....

 

if it hasnt got a make on it, its prob a cheap poor qulity one the spring might not be closing properly