Truck Repair: N14 exhaust manifold leak

Question
Replaced 99 N14 with a crate engine. Rebuilt after 80 thou. ( water pump failed. Scored rear two liners )
Works great except for exhaust manifold leak. Tried factory and aftermarket manifolds. Leaks at joints,not a lot but enough that it reaks when a/c or heater on while stopped.  Used VersaChem joint and crack sealer at joints. Works great; for three days. Is there a wrap type product or something that can stand up to Commerical on road use?

Answer
Are they still leaking after then engine gets hot. The way that manifold is designed it will leak for a little while til the engine gets hot once it gets hot the joints swell to seal off. As for your question might look up high performance auto parts they sell a kevlar type wrap that helps to lower your header temps might work at sealing out exhaust fumes.