Hi Pete, is a wastegate the same as the dump valve???
On my Volvo 440 I could hear that sucking and hissing away, I cant say I've noticed the same with the L series, did squirt some WD40 around the adjustment arm to see if it was stuck.
The turbo kicks in OK, just dont get the suck and wooosh noise.
Your one is much too technical for me, just about know how the derv works, but with the torque you are getting I bet it goes.
