I've discovered fumes and exhaust odors coming from the oil filler neck and dipstick tube on my recently acquired 2000 Formula. It's not lots of pressure or air but noticeable amount of fumes at the rate of a cigarette burning. I've had this problem due to an intake leak on my 3.8 which was sucking in water... as seen in this post if your interested...this is a common problem and can save you an engine....
https://ls1tech.com/forums/pontiac-firebird-1967-2002/1948277-omg-crazy.html#post20346136

Thanks to 98CayenneT/A for this...

Then if you pop your hood and put some water on the windshield it will be leaking here shown in blue dots




After it leaks here it's running onto the intake which either needs tightened or new intake gaskets because that's where the water is able to either pool in the chambers causing hydro lock when not running or causing the steam when getting wet while running
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...anyway, I checked my pcv and made a repair but otherwise it seems OK and runs good (besides a lumpy idle) with no codes, no exhaust smoke or smell, coolant looks good, oil looks good, fuel consumption is normal. I don't have any personal experience with this engine and wonder if this normal blow by or should I check something else.
Thanks