For your particular case, your only option is going to be to remove the EGR valve and clean it. With 200k, it probably isn't a bad idea to pull the head and send it to a machine shop to be cleaned, honestly. The flush I referred to in my RSX thread was in the crankcase, to clean up sludge deposits and whatnot - but that wouldn't do anything for buildup in the head/intake/exhaust. You're pretty much SOL on those fronts.
Sucking solvent in through a vacuum hose will do nothing for you. You can For the most part, additives are garbage.