I had loads of problems & it was the MAF. They go at 60k miles. take it off (2 min job) & spray it with tons of contact cleaning spray and the connector & lead. Mine was 90 % right after that which told me it needed a new one. Get the part no off it & buy one online & fit it youself. Mine cost me £ 100 over here - dealer wanted nearer £ 300. I really would do this before messing with the more technical stuff.

Good luck.

Nige