HELLO I HAVE A CHECK ENGINE PO171 WHAT COULD IT BE HELP

I'm chasing this myself on my 06 TB. Start with the basics before you have a smoke test done. Make sure there are no leaks post MAF sensor. Clean MAF sensor. Make sure intake bolts are not loose (very very common). I've done all this, will have a smoke test done next, which should reveal I have a cracked intake manifold (it's plastic!) or leak there.