I bet you money it's not just the cam chain tensioner, that wouldn't generally cause a power loss until the valvetrain's squashed itself (an SV can run 10 degrees out, from memory, but what are the odds of it jumping just one tooth? Pretty slim), which is what I reckon's happened- not actually all that difficult to fix though. I wish I had space to take it on, but I don't
But, if anyone does take it on and ends up wanting a hand, then you know where I am, and I've also got most of a couple of engines (including one Paul sold me!) so unless it's crank I should be able to help out with bits... Might help.