Holy Motherf*****Theresa!!
Nobby, you don't want to be hanging around mate. As I understand it, if you've got a blocked wastegate, then it's only a matter of time before your valve pops right the hell off. A man I know was unlucky enough to have both a blocked wastegate and a stuck pop-off valve at the same time, and that's a world you don't want to be on, I promise you. When his system finally reached a critical point of over pressurisation, he found himself in terrible trouble. I can still remember seeing his eyeballs rocketting in formation over the rooftops of the street opposite.
I think the moral of the story is to keep your pressure relief pop off valve in top working order, and there's various lubes that are just the job, as I say, it's imperative that your circuit can be freely vented.
You may want to consider fitting a breathing circuit via some large diameter surgical tubing, although for sweet Marys own sake don't let the pressure in the breathing circuit rise above the systems internal pressure, or there could be some very embarrassing blow-back.
I speak from personal experience of these matters, and I hope this has been some help. (of course you could just hit it with a hammer, or, as matron used to do, touch the end with a very hot teaspoon)
Regards
H
