vacuum problems

I have a 1994 bravada and it has a little power issue and when you put load on it like going up a larger hill it gets a little doggy ond if the a/c ar hetter is on vent it will go to defrost by its self. Dosent seem to be any vacuum leeks and it has a new cold air intake,o2 senser,cat,muffler, botch platnum+2 spark plugs,wires, and a performance chip. Any help would be appriciated. thanks.

It does sound like a vacuum leak.

I have a 1994 bravada and it has a little power issue and when you put load on it like going up a larger hill it gets a little doggy ond if the a/c ar hetter is on vent it will go to defrost by its self. Dosent seem to be any vacuum leeks and it has a new cold air intake,o2 senser,cat,muffler, botch platnum+2 spark plugs,wires, and a performance chip. Any help would be appriciated. thanks.

Welcome to AF.
How big and how long is that hill or mountain?:grinyes:
What engine and PCM or VCM and what dist flat top or old style.
If PCM and old style dist have you set the base timing?
Put a vacuum gauge on it and give us the vacuum readings at idle and at 2K rpm.
I would pitch the Bosch plugs in the trash can and get a good set of AC delco plugs.
What kind of cold air intake?
Is the air intake tempt sensor on it and working?
I would also go back to the OEM chip and see if it has any more power.

How is the fuel pressure?
Any engine miss.
Any check engine lights?

On the heater AC problem check the vacuum line from engine to vacuum tank and from vacuum tank to heater controls.
But that is a different problem from engine running.
MT

The hills are just average. It has the 4.3 vortec,vcm and has the olds syle dist.I got a k/n intake air tep sensor is new and works. new fuel pump and filter and has 55 psi. no service light and no miss. I just figured that there was a vacuum problem because the air vents only cut out when i step the gas down.

Yes you have a vacuum problem to ac heater controls but it is a different problem from low power.
On engine power.
Start with pitching the bosch plugs and check base time.
On fuel pressure you should be seeing 55/61.
On the road on a pull you should have 60 lbs pressure and also on a cold start

If you have to keep your foot in it to get up the hill because of the low power problem then the vacuum/heater/defroster is a symptom along with a leak somewhere. The leak can be nearly anywhere in the system going to and including heater controls.