Dont bother with the MAF or larger throttle bodies. Its the resonator above the TB and the rest of the plumbing that is killing your airflow.

Sort this out and its worth up to 25HP (seen on my local Dyno, with a Focus with a custom intake). Thats with the 60mm TB and standard MAF

Laminar fast flow is more important to the Zetec than volume. Larger flow means lower velocity and more turbulent flow and less power. you want long smooth fast flow

Mad Mole
Visit Mad Moles Mondeo Madness
2L Zetec, Cams, Stage 2 head, Valve work, Powerflow, Unichip, AEM Ram, K&N, Ecotek, 75mm Lower etc.
192 BHP, Faster than a speeding Duratec!