When I remove the oil fill cap (F23A1) with the engine running, a lot of "air" blows out from the fill hole. As if there is small blower inside that is blowing the vapors out. Is this normal ?

 

thats seems normal all my other cars have done the same. and you can somtimes see the small hint of smoke coming out aswell...never helped me lead to think its somthing wrong....

 

That's normal unless it feels like a wind coming out, that could be a sign of blowby if it's excessive. But normally it's just the air being displaced by the pistons

 

well it is certainly not a light gentle movement of air. It is fairly strong. You can feel it hit your hand pretty good about 6" from the hole. Definitely much more than my other car which is an Acura MDX (3.5L V6 engine). Let me see if I can post a audio or video of it...

 

Well it's going to sound like a loud muffler. that part is normal, a leakdown test might be in order

 

yes thats right. sounds like a muffler as soon as I pop the cap.
will a compression test tell me if there is a problem ? I know it wont tell me "where" the problem is but I'd be able to do that much quicker than a leak-down test.

 

A compression test won't be as accurate to your issue as a leakdown test but it could help out some