My 07 GTI started throwing code P0171 so I started with the MAF sensor and now I'm getting P2187 which I believe is to rich at idle. I've done everything I can to check for vacuum leaks and haven't found any. What and where is the next thing to look at.
Let's get more specific. You changed the MAF? And immediately you see the P2187? What time has elapsed between the new MAF and the P2187? Have you cleared the codes and found the P2187 returns each time you drive it?
Both mean System too lean, with the latter, P2187, meaning too lean at idle.
Both can be caused by a leak and/or the MAF. If you replaced the MAF...that would eliminate the P0171...but it still is detecting lean at idle. It is possible there was originally more than one issue.
Now, with the MAF replaced, it is most likely to be a leak or a B1S1-O2 sensor. If it idles rough, it is a major leak. If it isn't idling roughly, then it may be a small leak or the O2 failing. Have you tested the engine vacuum at idle? Have you smoke tested it? Or pressurized it and tested with soapy water?
It is possible the EVAP N80 is failed or there's a leak in the EVAP system. You can test the N80 with a vac pump w/gauge and also the EVAP system with VCDS (there is at least one DIY vid for this).
Leaks can also be;
oil filler seal (seepage would be noticeable)
cracks in the intake manifold's seams
brake booster tube
pcv valves, pcv tubing, and/or rear crankcase breather tube if valved