terrible engine noise in TR6

[Rob C Swift <RobSwift@PetCentre.com>]

Eric,

I also get a sound from the passenger foot well of my TR6.  My sound is 
more like a farty-exhaust like noise that sounds very much like a VW bug. 
 It only does it when there is a strong load on the motor, say when 
accelerating in too high a gear.  The sound began all at once earlier this 
year while driving the car after a long sit.  It does not seem to be linked 
to a specific engine rpm as you say in yours.  Does anyone thing these are 
similar problems?  Any help would be appreciated!

Rob Swift
'75 TR6