I have, but I am concerned that maybe the cracked exhaust manifold may throw off the a/f to the point where its shortening the lifespan of spark plugs, o2 sensors, and maybe the catalytic converter. I do hear the vtec, yes, its actually more noticeable than ever. I know typically, where I have stock exhaust, I really hafta listen carefully to actually hear vtec engage, now its very noticable, and you feel the car instantly lose power under vtec. Friggin wierd