On the back of the extender, are there not switches that set the high/low output? I know the newer NG extenders that Philips built have DIP switches on them. The switch positions are normal and high output, IIRC. If you want to control the level though, I think you have to use stick-on emitters and not the IR Blaster which is what I think you are using.

One thing you can do is to put a black piece of electrical tape over the sensor area but prior to placement, punch a small hole in the tape. This has worked for some.

Lyndel