Hi Bruce, thanks for your comments. Interesting whether the improvement is down to the K& N free flow filter or the cold air tube - probably both, but I wonder whether the length and routing of the convoluted tube is any less restrictive than the trumpet. I may try a half way house with a K & N inside the canister to replace the paper element if there is a noticeable loss of performance.
I can't answer scientifically your assumption regarding airflow through the tube but from observation of dust and grit collecting in the canister after driving through the desert then the airflow is considerable, I use a racing rain sock to keep the filter clean. The issue with the trumpet being in the engine compartment as well as restriction is hot air being drawn in.
