Has anybody bought/made one of the above for a Zetec? Seemingly all of the proprietary units are 4-1 which is OK for top end but tends to mess up mid-range torque. Comments?

4-1 isn't a big problem but I would always go for a 4-2-1 as basically and in simple terms "it's better" (all the gain of the 4-1 without the loss of midrange)

I have the same issue with my vauxhall 16v which is why I am making a manifold (eek, big expensive job, but less than the £500 that decent places want to make me one!)