You could also check junkyards for a cheap replacement manifold. Most of my local yards sell them for $25-$30. I do see a lot of cracked ones in the various yards I frequent, but most look good. The cracks usually form right up front under the air slats in the heat shield so if yours cracks, you'll probably be able to see it (and hear it). My original had a 3-inch or so crack with only a tiny gap and it was very loud even at idle.
When you do the timing belt, you might consider changing the front crank seal and both cam seals. Super easy to get to while everything is off. The seals on mine were hard as a rock and cracked into pieces when I removed them.
