I'm getting quite a few codes. EPC light on, Engine management light on. Codes P300-P304 misfires, P310B low pressure fuel regulation, P119A fuel pressure sensor, P2279 leak in air intake, P507 low idIe. I have carried out all the following work below to my beloved A5 and nothing has changed. I would really appreciate some insight to what I may try next if anyone has any ideas. Its the fuel pressure codes that I don't understand as I think I've addressed everything.

I have replaced the low pressure fuel pump, ECU for lift pump, new high pressure fuel pump, replaced fuel pressure sensor twice. Traced fuel pressure sensor wiring back to ECU, Replaced all fuel injectors, inlet manifold gaskets, new spark plugs and coils. Replaced camshaft sensor, MAF sensor and new PCV. Cleaned throttle body. Cannot seem to find the problem. 195k on the 2.0T engine on my A5 Quattro.

The car drives well, just idles bad, exhaust smells and fuel economy is crap. Idles ok if I increase RPM by turning on the AC or putting into gear. Any ideas on how I should proceed next? I am resisting taking it to Audi for obvious reasons. I am using VCDS for the OB2 scan tool, so could there be more tests I can perform to point me in the right direction?