Surging when braking in garage - scary

I am having a surging  problem with my '98 Silverado (5.7L with 107,000 miles).

As I drive into the garage and lightly press on the brake, sometimes the engine will surge and I have to clamp down on the brake.  Needless to say, this is a little scary - I'm afraid I am going to fly through the back of the garage.  It seems to be more of a problem when I just ease on the brake.  It also happens while at a stop light or stop sign, etc.  Does this sound like an Idle Air Control Valve issue?  I recently put some Gumout in the tank which seemed to help, but I don't know now.  The weather has been very cold lately, and I wonder it that has something to do with it since I haven't been driving it very far from home to work (changed jobs).

I have both a Haynes and Chilton's for my truck.  The replacement looks pretty easy.

Before I went and just replaced it I wanted to see what other thought it might be.

Any help is appreciated.

Well, it happend.

I flew through the back of my garage tonight.  Mostly damaged the wall more than the truck. 

Ouch

It could be that but I would check the knock sensor too.  They can cause that.