Exhaust already breaths enough for 135hp or so, so most of the work is on the intake. Stock manifold is pretty restrictive, but sidedraft manifolds are easy enough to get. Just takes some careful porting on the intake, new valves, and a good cam an you're at 125hp knocking on 140.
That or turbocharge an megasquirt it like I'm planning. I was hoping for 185 but last estimates put my project motor as easily exceeding that.
Of course the Miata drivetrain in the Opel would make power even easier to get.....

