countryaggie , yes lots of options
Exhaust Manifolds
-6.0 exhaust manifolds -better then stock more air flow ,can get these for 50-150$
-MPD maryland diesel performance logstyle , need uppipes ,no dyno proof but have been installed and have been proven on many trucks -around 700$
-Dirty diesel - also log style ,need uppipes , unsure of performance ,2K
-RCD new on the market ,simliar to the stock 6.4 mannys but no restrictions , will run you around 900-1000 ,plus uppipies
-No remorse - these are ss logsytle with a slighly smaller diameter pipe infront unlike the other logstlye where they are all same diameter piping , these are new on the market ,go for around 900$
-Steed Speed - these are not proven yet and are under reasearch to iron out the issues , these will run you 1000$ plus uppipes
-Darkhorse ?
There are more out there ,please chime in and add to the list , you can also wrap some mannys for heat or have them coated , i havent seen testing on any other then SS , but all are much better then stock as far as flow!! Most of the aftermarket manifolds will require use of uppipes , (Darkhorse diesel has for around 600$)