Well, as you will find in about a million previous posts, the driver's side header is the problem, due to the fact that the steering shaft is in the way. I have read that the stock scoupe manifolds can be ported to flow as well as the mustang stock headers. I am not sure I beleive this, but it is what I heard. I decided that they were both restrictive and went with a set of 1995 mac shorty headers - 1 5/8" primaries and a 3" collector......major modifications. I heard that the 2001 mac shorties are easier, but you have to beat the crap out of the collector to get MINIMAL clearance for the shaft. If you are not looking for alot of power, stick with the ported ones.
John