So I have a question.

My car has a pretty bad exhaust leak which is getting fixed tomorow. the leak is occuring where the manifold bolts to the hotside. Any way while I was getting on the highway to go to work today the car felt sluggish. I didn't feel any boost until about 5k in 3rd gear. (merging on the highway). Is the exhaust leak why this would be occuring or something else?

 

This type of "pre-turbo" exhaust gas leak is serious, nasty stuff. Since the gases in your exhaust manifold exhibit a pulsating pattern, there is both an exhaling of exhaust gases and an inhaling of unmetered air through the exhaust leak area. This alters the O2 content of the exhaust that is read by the O2 sensor. The leak allows "false air" into the exhaust stream which was never "read" by the MAF sensor.

The computer sees the exhaust as being too lean due to the additional, false air. So the computer starts adding fuel to correct this perceived "too lean" mixture. Of course, the fuel mixture becomes excessively rich due to the unnecessary additional fuel. Now the ECU responds by again pulling fuel, which creates a cyclical, "kneejerk" between too rich and too lean.

When you have such a pre-turbo exhaust leak you also get high knock counts due to the excessively lean ECU swings as the computer overcorrects. So you also get ignition timing being pulled by the ECU. So in extreme cases you can get boost cut and fuel cut and ignition timing pulled all at the same time. Not good

As a cautionary note: you´ll want to only use the OEM factory dull grey exhaust gaskets. Don´t use those shiny silver gaskets that come with aftermarket kits.