Could someone explain to me the vacuum system, how it works, why it is needed and some common causes for the leaks? I know nothing about this system and would like to learn.

 

That can take hours or pages to begin to describe that system, why do you ask, are you having a problem?

 

Yes I think I have a vacuum leak as my rover is "chugging" a bit after deceleration. I am currently replacing wires, plugs, o2 sensors, MAF, exhaust manifold, and brakes (plus tires) so I was hoping that these improvements help, but as I have no understanding of the vacuum system I am really at a loss. Are there small things to check? I checked the air filter and box, tightened the oil cap but I have no clue if these would even cause a leak I was just guessing.

 

Do you have a check engine light on, if not it isn't vacuum related.
Finish the tune up, do an induction cleaning and you should be fine if you are not burning regular gas.
If it is still there after all your efforts, get back to me.

 

Yeah I was throwing a bunch of codes. I posted them on here last week or so. Most seem to point to o2 sensors and maf. BTW: after reading about how easy it is to change brake pads, I might give you a call for a brief run through if you don't mind, and try to change them out myself to save a hundred or so bucks.

 

its pretty simple. as the pistons in the engine go up and down, they create suction on each intake stroke, and youre left with low pressure in the intake compared to ambiant pressure. air is then pushed from outside the engine into the engine and then burns and out the exhaust. all the air your engine breaths is a 'vacuum leak', its just monitored by the MAFS. when air is pushed in through a bad hose or something, its not metered and you have more then then it thinks you have. these engines also have a PCV system, so the crankcase is also a low pressure system so that oil fumes, and blow-by can be burnt and not just vented. on a d2, arent too many places to have a leak from, youre looking anywhere between the MAFS and the intake ports on the heads, you have a breather line on each valve cover, a secondary air harness(or a rubber plug if not SAI) and a fuel vapor purge valve.