I have a 98 Tour V6, non- SVT. Mine pulled a P1151 with a P0420. The dealer was concerned enough that he scoped it for me, reset the CEL and told me I had a bad O2 sensor (front upper). I replaced it and I pulled another code in several days, which the dealer again read for me. This time it read the code you had about the intake manifold being stuck. This time they replaced the catalytic converter under warranty, as I had just under 80,000 miles. I think the fact that with a new O2 sensor and the intake manifold code told them the cat was blocked - I don't know for sure but I wasn't going to question the free cat. (They even installed the rear upper O2 sensor, which I had purchased, while they were under the car doing the cat. Nice!)
What I am saying is if your Tour is under 80K have the dealer check the CEL code to see if you have the same problem I had. It is common enough that my dealer had all the parts in stock for the cat replacement.
On the flip side, I now have a CEL that indicates a lean condition; what could be a bad intake manifold gasket. That's aleast less expensive than a cat.
