as above error codes i get are 0500 and 0105

got these as speedometer error and inlet manifold pressure/map sensor

had the map sensor done a couple of months back and still i have the same problem went back last month and they said its to do with the gearbox, now thats sorted it should work fine.... but still cuts out after it drops below 1000 on the revs. got that booked in on thursday for them to check again

speedo i got told was run off the diff in the gearbox but the garage told me that its run off the near side abs ring or sensor

can anyone point me in the right direction of where it reads it from

i have a 1.4 16v 2001 astra

garage that did my gearbox said it could be a bad ground point somewhere causing all this trouble? could this be the case?

cheers in advance