Help with code ASAP please
 

my friend has a 98 Z28 stock and is throwing a P0171 code ( system too lean bank1) any ideas as to what may be causing this? He is also using 87 octane. thanks for your help.

look to see if the EGR tube gasket has slipped out of place and is sucking air in through it. mine did that a couple of times and would give the same code.

first, tell him to quit using 87, second, has he modded it anytime lately? Has he listened for vaccuum leaks? Exhaust leaks? (I'm guessing not...)