Phillip

Before you spend 1100.00 try a simple can of throttle body cleaner around the inside of the throttle body and on the valve plate. It sounds to me like the throttle is being affected by the build-up of "gunk" or carbon under the plate.

It will tend to allow the plate not to sit in the correct position allowing more air into the intake and thus the computer will try to even it out by adding fuel to the mixture.

The throttle cleaner costs at least a 1000.00 less :)

Have you ever cleaned this before now? If not take a look inside the throttle body and look at the plate. You are going to be surprised at the amount of carbon on the edge of the plate.

Mine is a 2000 S40 and it exhibited symptoms similar to this. Cleaned it and bye-bye surging.

Let us know what you find.

Miker