Mach 1 Heads Improved In Late 03 Models?

[CanuckMustang]

I'm considering buying a late build date 03 Mach 1. Is there any truth that Ford improved the heads (i.e. grinded exhaust ports) late in the 03 model year to improve performance? Supposedly the better heads have blue markings on them and flow noticeably better (as per a thread on Mach-1org web site).

I'd also like to know if the new exhaust systems on 04 models increased horsepower.

Anyone out there know the facts or have seen dynos that prove this?

I'd appreciate any help as I am looking to buy a new 03 or 04 Mach 1 right now.

 

[01GT/03ZX9]

no and no. The improved heads and blue markings are just rumors.Some '04's with blue markings still get the head tick.Go over to www.mach1registry.com and find out more.

 

[gruntman31]

I think the only real difference is that the 04's don't have painted valve covers.