Tagging this because I had Maximum Motorsports Full Length Subframe connectors welded into my 99 Cobra (SN95) and it made a WORLD of difference.
From what I have been reading, some folks claim that the s-197 chassis is plenty stiff and they are not required , others claim that it still does improve handling and eliminates chassis flex.
Even Steeda claims subframe connectors are not necessary on s-197s?
"We spent countless hours figuring out where the S197 Mustangs could benefit most from chassis stiffening. Here is the end result. There are several vendors out there treating your S197 like it was an old fox body, making large braces for areas that are not weak on your S197 and that add a lot of unnecessary weight.
We took a strategic approach with Steeda's 3-point torque box and frame rail braces. These braces are made from 4130 Chrome Moly material. This material is twice as strong as mild steel and half the weight of mild steel.
These braces are compact and light weight. They are much lighter than the unnecessary braces many competitors offer and specifically designed for the needs of the S197 Mustang. They tie together the inner/outer frame rails and the rear lower control arm mount. One of the few areas on the S197 that could use additional bracing.
Our braces are silver powdercoated and come with mounting hardware. They can be bolted with our supplied hardware or welded in place for maximum effectiveness. "