Does the valve spring issue occur in 2000 model 500hps that are carb'd?

I THINK SO MINE WERE BUILT IN 9/99 NEEDED TO BE DONE!!

Yes, I had some broken inner springs at 158 hrs. 200 HP 500 Carbs. And just an FYI, I ordered the replacement springs Teague recommended in his Powerboat article (can't remember the manufacturer off the top of my head). Got them back in March and the quality was poor. My engine builder noted 30lb differences in the spring pressures after only 10 hours of use. Not sure if others have had similar experiences with poor quality springs, but may want to check. Could have been just a bad set I got, but I would check it out.

How would I know when to do mine? What symptoms did the engine have?

Went with Isky 8205plus endurance springs on my 2000 500EFI's @155hrs and yes the originals were sagging, although they probbly would have made it to ~200hrs.

I think your supposed to do it before there are any symtoms.

If they were sagging, did it run better with the new ones? Or they just needed replacement?

I just did it. Did the head gaskets too, which would have never made it through another season on one motor in particular. It did run better, probably because I bumped the rev limiters up at the same time though.

Mainly the power starts laying down....then if you pull the valve covers you'll usually see a broken spring as the cuplrit. Make sure you look at the inner springs also....

Nothing noticeable when running the engine (at least on mine). My head gaskets weren't going to make it another season either. Agree that you should check the inner springs, that's where my broken spring was.