e28/m30 exhaust leak?

[Doinitin3D@xxxxxxx]

   My 535i has a strange sound which changes "timbre," for lack of a better
word, depending upon rpm/throttle.  The sound is coming from the engine/engine
compartment or exhaust, and does not change pitch, so much as it changes
amplitude.  (Like when you make a "whoosh" sound with your mouth and vary how
far your mouth is open - it is VERY difficult to explain, for me, anyway!)  I
am assuming that it is a manifold/manifold-to-converter leak (the flange joint
has been checked twice...).  Could I have a failing manifold/head gasket?  I
have next to zero acceleration until 3k rpm, at which point the valves become
very loud, and there is a pronounced power surge...  Any help would be greatly
appreciated, as hibernation season is ending soon!  PS>  It's an '85 535i,
142k miles, brand new cam, new rockers...  Drive crazy  }>)    rob

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