07 Versa acting doggy, getting terrible bad gas mileage...did I do this?

[spunky_monkey]

I have an '07 Versa with the CVT transmission. ~37k miles and we've had great luck with it, so far. We've kept up on oil changes, getting them as recommended.

I started trying to do some of the maintenance myself and am wondering if I caused a problem. A few weeks back, I decided to replace the engine air filter. It was super easy to do and I was feeling like I saved myself money. I bought a filter from Checker (KLM?) and popped it in.

However (possibly coincidentally), now the Versa has been acting different. It accelerates slowly and the engine seems to be running roughly. It no longer has the power it used to have. Instead of my normal 31 mpg, now I'm getting around 25.

Hubby assumed I might have put in the air filter wrong, but we checked. Installing the engine air filter seems pretty idiot-proof. Only 1 way to put it in, and the filter-holder can only fit in a certain way. Anybody ever heard of a bad engine air filter? Would this cause a problem like this?

I've been doing a little reading online, and it looks like some Versas have had a fuel pump problem. However, the car never really has issues starting or dying. It's just sllloooooowww to accelerate, and then as I accelerate, the RPMS shoot up and then drop back down.

I'm taking it into the dealership tomorrow to get them to check it out, but thought I'd try to go in a little prepared. Any suggestions?

[NODES]

did you accidentally hit or jolt the MAF sensor?