Wet nasty black soot.

I guess this really doesn't have to be in International but since that's what I'm driving I'll start here. Driving a '06 9900I with dual stacks that project just over the sleeper. Been driving it since November of last year and when i first got in the truck it already had black crud all over the top of it and down the stacks. owner of the truck said it was from an oil cooler issue in the past and it just does that every now and then. I took that with a grain of salt, truck went down the road and my checks cleared. so not a real issue. It took me awhile to put two and two together that every time it rained hard and i wasn't idling the trailer ended up blacker than it started out. Yeah I can be a real rocket scientist sometimes. So after a bit of research I'm pretty convinced it's just wet soot that had nowhere to go but up and out when I hit the throttle.

I have looked and cant find a drain valve anywhere, which to me, seems a bit retarded. I've looked online to see if they even make inline pieces that can be installed that have a valve and cant find anything. I've read about other drivers just drilling a couple quarter inch holes at the lowest point of the unit, but doesn't that defeat the whole 'no exhaust leaks' thing for when DOT is trying to find anything wrong with your truck?! Although it makes sense.

I can somewhat control it now, either I idle while It's raining hard or idle for awhile when i get up to cook off the moisture before I attempt to hit the throttle. But occasionally I didnt even know it rained, and dont have much time but to check the fluids kick the tires and check the lights before I roll out. and It does nothing for when I go and get a nice sparkling clean truck at the beacon. By the time I'm five feet out the wash bay I have black crap shooting out.

I'd like to get it home disconnect the flex at the bottom of the stacks and pressure wash the heck out the stacks and let em air dry before reconnecting. I think that may reduce the amount of junk I have shooting out now but It really isn't a solution, just a band aid.
Any thoughts?

 

yeah it's an ISX, and they are curved. Not straight pipes.

Where would i get the Boost and EGR cleaned? international? any idea on cost?

 

okay, finally back home. Gave the truck a bath and now that i know how to semi prevent it should be okay, however both me and my boss are looking at ways of eliminating this problem for good.
His idea is to reroute the dual exhaust to a single running out the bottom. Preliminary inspection says roughly 250$ in parts. sounds great. A) I've only seen the newer trucks running the exhaust out the bottom. Is this a legality issue , say since their running DPF and or DEF, it's okay to shoot them out the bottom? or does it not matter? ( I really am a knucklehead when it comes to these types of things) B) will it affect performance at all?
Also as a secondary idea, I saw a truck, have absolutely no clue where, that had stacks that fit over straight pipes ( so the main exhaust (straight pipe) continued up into these 'tips') and at the point where they connected they curved out maybe 3/8 - 1/2" and around that curve there were manufactured holes to let water just go down the pipe. Has anyone seen these? or know where I can inquire about them?
Thank you for you help and consideration.