[s-cars] air leak....poor performance

[Bill Clancy]

Hello all

I have had what sounds like an air leak for a couple months or so.    I have looked for it a few times but I cannot seem to find it.    The performance is poor -- feels like 75% of what I used to get, and I get shitty gas mileage too.    

Can anyone suggest a place to look for it?   

I think I have ruled out:
- the bypass valve (new again)
- the michelin man hose (replaced with Samco and appears in tact) 
- the plastic hose before the michelin man hose (appears in tact)

What other typical failures can cause an audible hissing noise at WOT?   

thanks,
-Bill