For about 2-3 months my 2011 Enclave has been missing/skipping during acceleration. The best way I know to describe it is it acts like it has bad gas or a fuel filter is clogged. Slight acceleration and it shutters, but you can punch the accelerator and it will take off. I took it to a GM-certified mechanic, he ran his scans and could not find anything. I did the same thing with a very reputable transmission shop. I have ran fuel additives through it, and thought to replace the coil packs but was told that would show up on the scans. There is no check engine light. My next stop is back to the dealer, but would like to avoid that cost. Car has 147K. Any ideas?