posmercedes

So, I'm no genius when it comes to mercedes..
We got this car (used obviously) about two weeks ago, and it's been running fine until today. We hadn't used it at all as of yet today until about an hour ago when we were going to make a trip out to run some errands, and after we started up the car and tried to accelerate, it hesitated for 5 seconds or more depending on whether we were reversing or driving forward... And in addition to that when we were driving, the engine would start to lag, and sound like it was revving over and over to try to catch itself back up, without actually doing anything, and then it would catch and run smoothly..and then after another 15 seconds or so, it'd do it again. We stopped at the local right aid and popped the hood and there was a brief cloud of smoke that came out from the back of the engine valve cover (or in that general area) but we couldn't figure out where it was coming from.. On the opposite side of the engine, though there was a cracked hose (i have no clue what it goes to) but no fluid was leaking out of it, so my guess was that it was a vacuum line? I haven't the slightest clue what the hell is going on with it, so please if you guys have any suggestions or idea of what it could be lmk (( btw its a 89 300E ))