[TTopJohn]

You've already gotten good advice here - the problem is likely unmetered air entering the system somewhere, aka an air or vacuum leak. Once they track this down, all will be fine. It can also throw off your gas mileage. The SRX doesn't get great mileage compared to a car, but compared to other SUVs of the same size and weight, it's competitive. Particularly if you compare it to SUVs that are as fast as the SRX - basically, Porsche Cayenne V8, Infiniti FX45, things like that.

Don't worry that this problem is somehow indicative of how your complete ownership experience is going to be. You bought a used car, and it happened to have a problem that needed addressing. It probably had this when you bought it, but since the previous owner was selling, it wasn't something they bothered with. This is pretty normal. Every used car needs something. But once you get it fixed, it's fixed. It's not a situation where because this problem happened, it will lead to other problems. Well, if you don't fix it it could, but it sounds like you are on top of it.

So don't blame the SRX, blame the previous owner, be persistent with your mechanic (or find another if they aren't fixing it) and get this taken care of so you can put it behind you and enjoy your badass Northstar SRX.