codes problem shooting on 2005 Ford Five Hundred

i got codes for p0109 p0191 p0171 they all point to something with the air intake what would be the first thing to check?

Asked by for the 2005 Ford Five Hundred
the large hose from the air filter to the intake has a couple of small hoses that come out from it. make sure they are all secure and tight. the 171 is a vaccum leak code for trims.
Roy
5 answers
check air filter first then mass air flow sensor
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i got code po193
were is the air intake at