Have a Maggie? Got a P0308 code? Step inside.
 

I have 2010 Camaro SS with a Maggie.
A few days back I got an SES message, an intermittent P0171 code and a consistent P0308 code.
Idle was a little rough but would clean up once it went above 1400 rpm.
I did the normal checks: sprayed carb cleaner around the manifold looking for a vacuum leak, checked the plugs and wires, swapped around coil packs and even replaced my front O2 sensor. I finally gave in and called a friend that works at a Calloway dealer.
He pin pointed it almost immediately, seems he's seen 3 other Maggie blown Camaros with the same issue.
Way back behind the blower, behind the rear belt drive and a bit off center is a very short vacuum fitting. It's maybe 1/4" tall, and has a thick rubber cap over it.
Over time the cap deteriorates and creates a vacuum leak on the #8 cylinder.
Replaced the cap and no more issues.
I thought I'd share this so that anyone else with the issue could avoid some of the pain I had.