I cant think of any reason why this should happen only when turning right (or bumpy), except that it must be some sort of loose connection. Especially if, as you say, the problem was cured temporarily when you repaired the MAF wiring.

I suspect the MAF wiring needs a closer inspection and if the wiring was 'repaired'... it may be a good idea to re-check the repair or even replace if possible.

 

I think Mr Squirrel is bang on there.

 

Thanks for the reply Mr Squirrel. Yes your advice seems logical. I shall strip back the rest of the wiring over the weekend and see if there is any further damage. The wiring that has been repaired is definitely not the culprit though as I cleaned the wires and then re-soldered the joint - it had broke at the point where it runs over the injectors.

Is there a way to actually test to see if the wiring in the sensor is ok - I have read previous posts saying that the sensor just unclips but mine is a sealed unit

 

Is there a way to actually test to see if the wiring in the sensor is ok - I have read previous posts saying that the sensor just unclips but mine is a sealed unit

I personally dont know of such a test but i would suspect there is one. (anybody?)
I cant say that i have heard of a sealed MAF sensor before. They are usually accessable and when exposed, are just a thin wire that can break easily so cleaning them is a delicate operation.
If you suspect the MAF sensor itself to be the issue (plausable, im sure - if the wire is broken, it could be making contact for the most part but moving under heavy cornering) its a fairly cheap part to replace at about £30 iirc.