I finally had time this weekend to replace my intake manifold and do a carbon cleaning of the intake valves. They sure needed it. This is 72k miles of buildup because the dealership cleaned the valves at 74k. The buildup is worse than the pictures show. I hand cleaned the majority of the carbon using picks and carb cleaner. I followed up by walnut blasting using a modified blast gun with a brass tube nozzle and a 3D printed vacuum adapter I picked up on ebay. The walnut blasting worked amazingly well and I'm extremely happy with how clean the intake runners are.
Full Flickr album here.
Valves before and after:
Here's the blast gun and vacuum adapter setup I used. I ended up cutting the nozzle down to about 6" to allow for more maneuverability. The nozzle is 5/16" x .014 brass tube (K&S #8133). I tried various nozzle diameters until I found one that would work effectively. Even the smallest diameter change made a huge difference here. I epoxied the nozzle into a brass barbed hose fitting that fit into the gun perfectly.The process was very clean despite shooting about 10lbs of walnut shells.
Intake and injectors removed from car.
I had these silicon plugs laying around that I use for powder coating. They worked perfectly to plug the injector holes.
Transferring fuel rail, sensors, throttle body, etc to new manifold:
Fuel injectors ready for new teflon seals. I borrowed the seal install tool from a local forum member. Thanks again Mark!
The only thing that really tripped me up is the new breather hose that comes with the updated manifold. The vacuum line attaches to the back of the valve that controls the runner actuator (right side of manifold) and the other end of the line bolts to the cylinder head between cylinders 2 and 3.
As for results, there was a noticeable difference as soon as I started up the car. Idle is much smoother, the car revs more easily and smoothly, and I probably picked up some power and gas mileage. I'm very satisfied with the results and will be doing this again in 50k miles.