M1009 Crankcase pressure increase

So I have a stock M1009 that I have put a KN filter and 40 series exhaust on. Now because of the increased air flow I am building up more crankcase pressure as evident by the seepage from my rear main seal. The seal needs to be replaced as I want my truck 100% leak free which it almost is. When I put the new seal on I will still have the increased pressure so the air flow increase is just making the problem more prevalent. I have been looking for a replacement breather/oil cap but can't find one. I would like simple fix as I want put a cold air intake on but haven't because that would increase the crankcase pressure even more. Thoughts?

Your CDR valve is probaby plugged up with gunk. It can be cleaned, or replaced. The breather cap can be cleaned with brakeclean. If it's missing alltogeather, it can be easily found at a local junk yard. The crankcase pressure is caused by blowby, and is common on all diesel engines. It is no cause for alarm. Fix the CDR problem and run it.