today i was replacing the hose that goes from the bypass valve to the S/C inlet right after the throttle body and when i took off the throttle body the supercharger inlet pipe is loose. is that normal? is the inlet pipe of ur r53's loose like that also? it has me worried becuase when i let off the gas i get a blow off valve like sound. the car runs fine BUT i used to get 24 mpg now im running 14 to the gallon. and i put factory plugs and a new filter. i should be getting a little better at MPG's. . and the car is back firing more than normal. any ideas?????

inlet pipe is loose

Air coming from inlet pipe must tight and pressurized.

how can i be sure that the blow off sound is coming from the inlet pipe? and the car idles fine also.

does not make sense.

the blow off sound you hear, came from the release of pressure at the intake side (u can call this inlet pipe). At the inlet pipe, there is a device called blow off valve others called it bypass valve and some dump valve. They operate the same way.
There is a small vacuum hose connected at this device to know if the pressure needs to be released or hold on to the pressure.

if your inlet hose is lose & the air is leaking, you will not hear a BOV sound, rather you will experience lots of problems like bad idling, sucky acceleration and stalling.

If not leaking, you probably ok.

and the supecharger whine is ALLOT louder