Dear Joe;
What you say is true only for a stock 250 like he has.
However; On the 292 engine (same head) the larger manifold removes the added heat (2" pipe) generated by the larger trucks, when hauling heavy loads.
This holds true also when installed on the 250 for added "exhaust relief" and saves the cost of headers for (mildly modified) 'street' engines etc.
This kid's confused enough, let's don't make it worse.
Happy trails.
