[200q20v] S4 rear muffler ok?

[George Fairbanks]

I recently put a rear muffler from a 93 S4 on my 200.  The part numbers 
were the same except that the last letter was one higher on the S4 
muffler.  It fit just fine; the tailpipes are about 2 inches shorter but 
the mountings etc all matched up perfectly.  Can anyone verify that this is 
ok?  I ask because my car is running hot and lacks power but I'm not sure 
if this is related to the muffler swap from 6 weeks ago.  Is there any way 
to test if the exhaust is flowing correctly?

Frank Amaroso has an S4 resonator (middle muffler) for sale but the part 
number is slightly different.  Any advice on this one?

George
Boulder, CO