This video proposes replacing the plastic POS intake manifold with a metal intake manifold from a 1995 Buick Park Avenue - non-Ultra. Anyone here has tried it?
YouTube - Pontiac bonneville 3800 series I (Plastic intake leak solution).

I cant recall anyone doing that since ive been here, but maybe one of the older members knows something... check back later and one of them might chime in.

You could always substitue the plastic pos manifold with a nice alluminum m62 supercharger

I never heard of the Series 1 plastic mani being much of a problem like it was in the Series 2 but now I guess we know why 3 million old people drove the Buick'*. <grin>

There'* the issues of cost and additional modifications...

At least in my case...

I had some moke mechanic try to hustle me for a grand to change the manifold gaskets...

charlie319 do you have a car with a series 1 3800?

By the time the guy in the video gets through with that aluminum intake it will be all scratched up.

Well, if aesthetics is your concern, I'm sure a dremmel can buff the scratches out,,, In theory, you can polish the whole exterior of the upper intake manifold for a "Show" appearance. However, my concern is more about fitment as my '99 is a daily driver.

The information on that video is good but only helps people with series 1 3800 motors.

That video is of series 1 3800 motor and your 99 is a series 2 3800 motor with a totally different intake manifolds.

My old '92 came from the factory with that manifold.
Guy calls it a "steel manifold" in the video at 1:02 - LOL.

There were actually two different S1 manifolds. One was metal and could be substituted easily where plastic was originally installed. Although it really wasn't an issue.

The issue is on the S2 motor and in that case you can use the S3 L26 aluminum upper as a replacement. Although I don't believe it'* been documented here, lots of people have done the swap.

That would be a worthwhile project for a "how to" sticky since it seems to be a constant worry of our brethren...