96 Windstar - Code P1538

Our check engine light is on - diagnosed code P1538, IMRC for front bank (2)stuck open. The van is running rough. I read elsewhere that this is a problem with an actuator and there is a method to check for a vacuum leak. I tried to check for a leak but nothing seemed to happen. Any ideas? Should I try a fuel injector cleaner (don't know why this would have any effect)? I am open to any suggestions you may have. Thanks in advance!

More info. I read a few other threads about this code and I was able to check more thoroughly. I found the following:

1. When plugging the front actuator line, the rear actuator linkage would move a very small amount (1/8th of an inch or so).
2. When plugging the rear actuator, the front act. linkage would close.
3. When starting the vehicle, both actuators would close a small amount - 1/8".
4. When reving to 3000 RPM's and holding it there:
a. Front actuator linkage closes briefly and then releases.
b. Rear actuator linkage does not move at all.
5. Both actuator linkages will pull shut manually.

I suspect that the rear actuator needs to be replaced. What do you think? Should I replace both? The van has about 110,000 miles on it. If I have to remove the plenum, should I replace anything else at this time?

look very close at the linkage for the control to runner - have had the clips break and jam - use a vac. pump and test the acctuators for movement and put a vac. gage on the the line to acctuator and rev engine with a snap to open throttle (please don't hold it there and blame me when it blows) the vac. should change at the high rpm.