Beins this is a 3 valve engine, spark removal can be a pain, but i can give u some tricks that will help if u r interested. Is p0171 and 175 the only codes? I dont believe i have ever seen this problem. a rich and lean code set at the same time for the same bank. that is odd...i wouldnt think it would be fuel supply related beins its on 1 bank instead of both. But i could see fuel delivery to cause this issue. I have seen alot of trouble with injectors in this engine, but u normally have a missfire code such as p03xx depending on which cylinder is missing. I would recommend pulling the fuel rail up out of the intake. Leave the fuel lines connected to the rail and have some one turn the key on while u watch the injectors. There should not be any fuel to come out of the injectors with KOEO. If an injector does leak fuel replace it....
I have seen the electronic throttle bodies due some weird things as well, but they normally set dtc's as well/
I would also recommend watching the o2's and see what they r doing. R they running rich and then lean on bank1? What is really happening? U could have a PCM issue as well... Hope this helps