07 Cobalt SS Supercharged no start

Hi guys, I am looking to the cobalt Gods for some guidance. I was having an intermittent no start issue but it has developed into much worse. When I first got the car the cat was hollowed out and made it run like garbage. I got my mechanic to do a full 3'' stainless with new cat and muffler. Sounds great made it run great again. The car has zzp stage 2 upgrades with fuel injec and a tune I guess. About a month ago car randomly wouldn't start. Left it for a day, came back fired right up, I drove it around left it for a day or 2. Come back now it's in a complete no start condition and has been for weeks. The car has a few CEL's, one for a front 02 sensor, which I'm a bit fishy about because my mechanic replaced all the 02's when he did the exhaust. The next code is running lean, and large vaccume leak. I just purchased a fuel pressure gauge praying that it was just the fuel pump, but while cranking the gauge read 55ish psi which from what I've read online is normal? What else could I check from here? Can a vaccume leak cause a no start? Love my cobalt and just want to get her running again, thanks for your help guys