Not entirely ridiculous, it works all the same and then it can still be pulled apart for service instead of having one giant header-back peice. You could put fancy flanges on it to be "proper" but any method works so long as it doesn't leak! A $1 C-clamp has been holding my sections together for years now and since I had my Stromung y-piped, it was obviously crooked as all hell when we bolted it back up, so we just torched it to get it hot while it was on the car and bent it little by little til is sat perfect in the cutout. Nothing ridiculous about it
but yeah, if the o2 sensors are not fuctioning - that could also contribute to an erratic idle but the throttle cable should still be adjusted abit to your car anyways.