"John H" wrote in message

.....If you've gotten 10 years out of them, I'd replace them.

......but replacing the manifolds and risers was pretty
straightforward.


I'll second John's evaluation. Visual inspection of the riser, manifold, or
elbow will only reveal a small portion of the interior. Ten years is a damn
good run for a cast iron part, and continued usage (particularly when you're
already showing symptoms of blockage) is gambling with a very large
downside. Replace "em.