I've been offered to buy a 3" intake pipe with a MAF to go with it for a VZ 05 wagon Executive. Do you believe a 3" intake pipe (steel pipe) would be beneficial over the stock intake pipe? Please advise?

I would not recommend replacing the MAF in an Alloytec as this may cause problems. In regards to upgrading to a 3" steel pipe, under rear world conditions, you would be going backward in power output due to the considerable increase in heat soak.