Suspect air leak causing cold start lean backfire.

[pgboxters]

00 boxster s with 91k fuel trims go to zero when I give it gas. Runs good already cleaned throttle body. Haven't attempted to smoke test anything. This has been an issue for awhile so nothing I just did. Maybe some obvious places to check. Thanks 

[JFP in PA]

Smoke test it, that will save you hours of chasing your tail needlessly........

[pgboxters]

Ok smoke tested through the tee on the aos top,  no smoke noted leaking. Aos bottom hose was alittle rattling near the connection pushed in.  Smoke was in the intake to the filter but none under oil fill cap I guess that's separate . Data recorded 

fuel trim short term positive 14-16. Long term -3.1 , symtoms slight stumble on cold start no codes 

A bit of oil on the right rear wheel well frame.