2011 1.2 polo P0171

[bazzadataz]

looking for suggestions on what could be the problem here
car is a 2011 vw polo 1.2 60bhp
code comes up running too lean bank 1
i'll list whats already been tried to save time
MAP sensor replaced
both pre and post cat sensors replaced
cat was replaced but original back in as was nothing wrong with it
throttle body isnt the issue
and no leaks in the system
the car drives fine however when doing emissions test the car seems to momentarily drop revs every few seconds (typically between 200-500 rpm of a drop when trying to hold a steady rev)
when the fault code is cleared the engine idle's a little rough and the drop between revs when doing emissions test increases to between 700-1500 rpm
(just for absolute clarity when i say hold a steady rev i do not mean idling, trying to hold the car at about 3000 rpm and it drops every few seconds)
will be looking at timing chain next as they're known to stretch and also exhaust valve as both are known to cause this issue.
if anyone has any ideas as to anything else that could be the cause or has dealt with the same issue any help/suggestions would be greatly appreciated

[iichel]

Perhaps have a look at the egr system as well. The valve may not close properly. Do basic calibrations for all parts replaced, i.e. throttle body and egr actuators.

[bazzadataz]

thanks for the reply and sorry i didnt reply back sooner, ended up getting rid of the car as too many mechanics and specialists have tried and cant find whats wrong.
best of luck to the man that bought her (he knows the story behind her but still recons he can cure her, hope he has better luck than i did)