Im getting the p0171 code. i have changed the front o2 sensor and it still comes on. i reset the computer and it comes back after 15 minutes of driving. I dont know what to do now. i have a custom t4 setup. the first turbo went bad so while it was sent back we noticed a piece of metal in the downpipe that stuck up and we thought it was an obstruction in the downpipe so we cut it out. I didnt have the code until we did that. so im at my wits end!