heat cycling EM's, different question

[Ken Keith]

Hi,

I hope I'm not beating this thread to death, I'm just trying to get 
information, and maybe provide some as well.

I'm wondering about the heat cycling of exhaust manifolds.  A couple of 
responses I got from people using Dialynx manifolds suggest that they 
do warp, sometimes badly, but after machining back to flatness they 
don't do it anymore.

Perhaps the metal needs to go through this seasoning/heat cycling to 
get settled down into their final shape.  I'm considering a used Dialynx 
manifold, so maybe all or part of this settling in process is already done. 
 
Reminds me a bit of the depreciation hit taken by the original owners of 
many of our eighties Audi's, the cheap prices have stabilized, or else 
our 5kcstq's would be on the market for a pocketsfull of change instead 
of $2-3.5k.

My question is:  Is having the EM mounted on a chipped turbo for a 
while, enough of a heat cycling to do whatever treatment to the metal 
that "can" be done to it?  Or, would some specific schedule of treatment 
provide further "benefits" (warpage to a final shape)?  IOW, if there more 
that can or should be done to heat cycle it besides just install it, drive it, 
warp it, and machine it?

For those with knowledge or opinions about thermal treatments of 
metal, does heat cycling offer any benefits that cryogenic treatment 
would not?  

For example, for the ultimate in stress-relieved/consistent metal, would 
some sort of active heat treatment beyond installation in a car have any 
benefit, if I were to do the cryogenic thing anyways?  If so, what would 
that treatment be?

My fear for any homebrew, kitchen oven, methods of heat treatment, 
would be that I would adversely affect the hardness of the metal and 
make it too brittle or too soft.  Perhaps this is more a function of the 
speed at which the temperature changes, as well as the maximum 
temps achieved.  I know if you quench metal it makes it harder, or 
softer?

Thanks,

Ken