First turbo spools but no boost till 4k rpm

[Cashpoint]

I\'m having in intermitent problem with the first turbo on my FD, in that it spools but until 4k rpm the boost is limited to .1 bar from the first turbo. When it does this if i lift off befor 4K I can hear the turbo stall as air comes past them due to the BOV not opening. Past 4k all is normal.

Other times the first turbos happly boost to 0.8 then at 4K the second turbo come on line and all is right with the world. It\'s driving me nuts as I\'ve checked the pipe but as it\'s not a constant problem finding a solution is proving tricky, could a waste gate be sticking?

[Bobbit]

More likely to be a knackered solenoid or one-way valve

[Cashpoint]

Where about in the system would i find them? Don\'t supose you know how much they are?

[Bobbit]

one way valves can be found on e-bay, search for viton valves, should be about £10-20.
Have a look here for trouble shooting: http://www.autosportracetech.com/RX-7/symptoms.htm