You're supposed to tell the dealer up front about a PIN. It doesn't hurt you to do that as the price with a PIN is fixed by Ford, not the dealer. There is no negotiating when you have a PIN.
What I found when I bought my 2008 F250 PSD is that different stealers gave me different prices for the *same* truck. I know it's the same truck because my truck was rare and I knew the VIN. Most of the stealers I asked covered up the VIN from the invoice, but I knew it was the same truck. So anyway, I had several different stealers fighting to sell me the same truck.
My local stealer, right down the street, tried to tack on about $1000 and they covered up the "X-Plan" pricing from the invoice. When I confronted them about it, they told me they'd throw in an alarm system and a DVD player. Guess what. I'm not paying $1000 for an alarm system and a DVD player that I can get for less than half the price.
I called the dealership who was the most upfront about the vehicle pricing, not adding anything they weren't supposed to add or were entitled to. I had them drive the truck to my house where I closed the deal and took ownership of the truck. In and out in less than 30 minutes.
X-Plan, if I remember correctly, was several hundred dollars above invoice. Just to see how well I could do without X-Plan pricing, I called one of the largest dealers in my area asking them how much they'd sell me a truck for similar to the configuration of the truck I wanted. I didn't tell them I had an X-Plan pin. They weren't even *close* and if I recall, didn't seem like they wanted to budge on pricing.