Hello has anyone got advice about light on my dash p0171 bank 1 lean. I have just had full exhaust system off and replaced all exhaust gaskets as some were leaking. Now I have got this code coming up. Were is the best place to start? 

Start with the cheap stuff, check for any leaks, post mass air flow, and pre lambda sensor, check breathers etc etc

Loud pipes save lives

Iv been looking to see if I had any air leaks and I think I have found the cause of the problem. Can any one tell me what this little solinoid looking thing is?? Definitely been sucking air. Would this be the cause of the p0171 fault code bank 1 lean?? 

That's the fuel system evaporation purge valve , supposed to recirculate the vapour in the fuel lines for a cleaner burn .

Its operated by vacuum,  so if it or its vac lines are leaking it could cause a lean afr.  Generally a vac leak would cause lean afr across all cylinders , not just 1 bank .

So if you've got a newage wrx check the Tgv's are operating correctly, as these are a common fault for fuelling issues on just 1 bank 😉

Again I appreciate response thanks. Do you recommend doing the tgv's delete. Should be straight forward as far as I can tell if I just take the flaps out and leave all the rest of the workings in place. I.e leave everything plugged in and leave shafts in. 

Unfortunately if you delete the Tgv's you have to get them mapped out but sometimes giving them a clean stops them sticking.