Would it be possible to pass the emissions test without a cat? any chance at all?

 

Without a cat OR a thermal reactor? No chance whatsoever. The design of the exhaust ports allows unspent fuel to be swept right out of the engine which is where the HC count comes from. Without any way of burning it up (thermal reactor) or chemically cracking it (cat....meow...), the stuff heads right out into the air like a proper Ecoterrorist would want....

 

You have about the same chance as a snowball's chance on a rotary exhaust system. Only thing I can think of that's hotter than hell.