Hi, am new here hope to have all the help i need in this place...
Ok as for you problem, i think it may be due to a faulty emission sensor or to another problem of this kind with the emission diagnostic (a short, faulty instrument panel pcb etc.). the way to know this is assessing the emission when the warning light is on with a professional mechanic.
Its could also be that the light comes on because the Gas cover is not well tightened, you have to turn it until you here the clicks.
It could also be a manifold valve that needs replacing...
So try checking that with your mechanic.
As for the Speedo meter, there is a sensor that is located somewhere on the right-side or the cylinder block let me look up some pictures, the sensor could need replacing....
Check G22...
I hope that helps