On the 1998

1. Upper intake manifold was replaced at 58,755 miles. It was replaced on 9/9/03. Is it possible the newer design of the manifold wasn't out yet and its still the old design that is prone to fail?

2. Lower intake gasket, this has to be done also correct?

3. Anything else I have to worry about/replace in the engine so it doesn't throw a rod or blow?

As far as we know, there is no GM-made UIM for our cars that has completely resolved the possibility of failure, yet. So, you will have to pay attention to your car and be aware that you may still have to do this repair again.

The best UIM replacement products out there so far are the Dorman kits and the APN kits. These both include heavier walls and reduced diameter stovepipes for a more likely chance that failure can be avoided, or at least delayed a lot.

Also, in 2003, the New style aluminum-framed LIM gasket had not been release, so you will still have to keep an eye on that, for now too.