Servo
, you mean vacuum booster?
any used sidekick should be a suitable
donor, try Hawks I'm sure he's got one.
I run the turbo and never had trouble,
but there is a check valve in there too.
Might be a rebuild kit available from
a good parts store like a Napa, call and
check, it's not hard to rebuild, it's just a
rubber diaphram that helps you stop, and
that's leaking.
Good Luck