Missing and backfiring through the intake?

I recently bought a 1992 BMW 325i that was not running. I was able to get it running, but it is not running well. It is missing and backfiring through the intake. When I press on the throttle there is a delay in response and will not run at a constant throttle position. I have installed new plugs which helped it run a little better. The previous owner did tell me that the car had been sitting for almost a year after his wife ran out of gas and he attempt to get it started by putting more gas in the tank, but was unsuccessful. Last night I was running the car and notice that there was a lot of smoke coming from under the hood only to find the lawn underneath the car on fire. The catalytic converter was apparently overheating and set the grass on fire. I activated the self diagnostic on the car and got a code of 1215, which is the MAF sensor, but I don't want to spend $200.00+ on a part that is not needed.

Do you have any idea what the problem could be?

Thanks.