Originally Posted by noah brinkman

If running over 7lbs. of boost an aftercooler (or intercooler)

is an up grade if you treat your turbo and it's components as a system
first thing is install a boost gauge to see what you are running for boost

your driving is different then my driving (I live in a small town in IL. no hills no elevation change)
so figure that out

rule of thumb for every degree of intake temp drop you can expect one degree of EGT drop

so we will assume a compressor discharge (air heats up when compressed) temp of 275

if you get an aftercooler efficiency of 70% and an abient temp of 75
in this example manifold temp drops to 135 degrees a 140 improvement

this would drop the EGTs about the same 140 degrees and eliminate any detonation issuse
or the possibility of any detonation ( I know we diesel lovers need heat to run but I got 22:1 compression and 405psi-410psi across all 6 cylinders in my 603.961 300 SDL)

example
pulling a cooler denser air charge can result in more power at less boost pressure BUT...
if your EGTs drop dramatically that differance lowers the available energy to drive the

turbos turbine (exhaust side) which slows down the turbine and lowers boost
but you could put a smaller turbine wheel on to compesate but who wants to do that?

So when sourcing a cooler many things to consider
can the people you get it from help you with your turbo SYSTEM

cubic in. (3 liter 183cu.)
boost you already run in your typical driving

RPM range you want to run "best in" (we diesel would be "low" 1500-maybe 3800)
my 603 can run up to 4500 then shift and bark the tires from 2nd to 3rd still got to adjust trans modulator it runs like a turbo 400 with a B&M shift kit and it shouldn't

sq. in of aftercooler equally (or close) matched to
RMP
horsepower range
turbo you have
displacement
fuel delivery amount (lite that candle)
muffler (get rid of stock) ( my muffler wears about the same pant size as I do 30in. maybe same inseam too 32in. ha!)
and don't forget about the air filter

example
sq. in. of filter required =
(lbs. of boost/14.7) + 1 x CID x max RPM/20,839
courtesy of K+N

So 10lbs. of boost 3L (183 cu.in.) 6,000 RPM max power (ours is lower but plug in your #)
requires 88.5 sq. in. of filter area

(10/14.7) + 1 x 183 x 6,000/20839= 88.53 sq. in.

I will put in a air to air after cooler maybe next year
an hour after shut down my intake cross over tube was still at about 130 degrees

I know that is the temp of the heat soaked AL. but can you imagine what the temp

of the air into the intake must be while driving!!
Cooler is better
cooler cars are better
cooler beer is better
cooler chicks are better
cooler denser air is better ( but there is a limit as outlined above turbine speeds ECT.)