Lean, backfiring, rough idle

So...I just officially joined the ranks of the proud LS1 owners with a 2001 Pontiac Trans Am. I've dreamed of owning this car since I was about 16 years old. I just flew about 600 miles and then spent the next 10 hours driving it back home.

Anyway, to the topic at hand, on the way back a check engine light came on with codes P0171 and P0174 (Lean). In addition to that, the car seems to be proned to slight back firing(nothing severe, just light popping and cracking) when down shifting or down rev at idle. The car has no problems running or starting but the idle is what I would consider "rough".

Any idea where I should start troubleshooting? I thought about taking a look at the MAF and IAT sensors and seeing if they were dirty but just haven't had the chance. Other than that, vacuum leaks seem to be pretty common problem but I don't have a smoke machine, is carb cleaner a viable choice?

Don't know a lot about the car but I know nearly everything is stock except for the SLP intake and Flowmaster catback.