I'm having a somewhat similar problem with code 1273. I think that I have narrowed the problem down to bank 1 injectors or the ecm itself. This code appears to be reported because of low voltage on AFS B1S1. I have seen the voltage fluctuation because of the brake booster but it makes sense because air from the booster is not measured. I think that I have figured out that codes 1273 and 1283 are catch all codes for any issue with air fuel delivery and trigger after out of spec. Voltage on AFS after a set time. I think that I am going to get more help with my problem since I don't have the tools to check out the ECM and I can't get to bank 1 injectors to unplug them to test against voltage on the AFS. Hope this helps someone.