[wiswind]

I have the walker direct fit "Y" pipe, bought through rockauto.
I will say that the best unit would be the OEM......lowest price I found was just over $1200, plus shipping.
List price for the OEM is about $1600.
The walker has been just fine......and was about $321 several years ago.

My personal opinion would be to leave the OEM "cat back" alone unless it is bad....surface rust not an issue.
I really don't think you will gain much at all in performance and economy in changing it.

One thing to keep in mind......performance = very low fuel economy.
On the post 1995 3.8L windstars, we have the IMRC which adds a good 45hp......but I can tell you for sure that fuel economy is in the single digits whenever the IMRC is OPEN.
That is one thing that has stopped me from trying to boost the performance of my windstar.
Although my plan would have been to work out a bigger opening into the air filter "box"......keeping the stock air filter setup.
That point.....where the air passes through the fender, is the smallest air opening in the loop at wide open throttle.
But, again.....what small gain one would get......would not result in any improvement in fuel economy.

We already have a "cold air intake" as the air is drawn in from the fender behind the front tire.
I have verified this by the fact that the air input temperature, as measured in the flex tube between the throttle body and the MAF.....is within a couple of degrees of the outside air temperature.

So, my opinion......for what it's worth, economy is about the best that we can get with the stock components.......in good working order.