stalling

My '96 350, SFI suburban keeps stalling on me. It all started a few months ago when the check engine light came on. The only troubles were lean system to both banks. I could'nt notice any problem, so I didn't do anything. Then two weeks later, I started the engine, let it warm up and shifted to reverse and it stalled. Then, I started it back up and shifted into reverse no problem. Same thing happened on a random basis. Now, when in park, and I apply the brake the rpm drops from 700 to 400. I didnt remember it ever doing that before. I almost wonder if applying the brakes is causing the stall somehow. And what can cause the lean fuel mix?

If you have a 1500 it has a vacuum brake booster. Have you checked
that for vacuum leaks/bad diaphragm. If it's bad it will allow air in and
lean out the mixture. Worth a look -- clamp off the vacuum line going
in to the booster and see if things change. Be sure to remember that
you have no power brakes when the line is clamped.

You know what, I can hear a leaky air noise coming from the brake pedal. I wasn told this was normal. I bet that is the problem. It is like a constant hissing sound. I will have to check that out.

Is your check engine light still on??

the check engine light goes off and on. I cant notice any type of pattern as to when it is off and on. It currently is off. The hissing noise from the brakes is constant and only quits when pressing the brake. Is this sound normal? thanx for helping.

Hissing from Hydraulic brakes is not normal. Leave the engine running, pop the hood and track down the hiss. Probably where you'll find your leak. Find your vacuum leak and you'll probably see that your truck runs much better. MAP sensor is all about vacuum and greatly affects how rich or lean your engine runs.
AutoZone will pull your trouble codes for free. Write to us before buying any parts and some of these guys can point you in the right direction.

well, the vac booster is definatly the problem. Thanks for your help fellas.