I've used Honda Top Engine Cleaner on mine after 75k miles and it worked well for me.
I did it again before my base dyno run at 105k (maybe overkill) didn't notice any difference that time. Honda recommends a bottle every 60k miles.
I've only put it through the intake vacuum line per Honda instructions on the bottle. And a bottle of Techron every oil change.
So far so good, 105k miles and 215rwhp on the dynopak!

 

I don't agree with this supposition.
This is too broad a statement with no substantiation.
You need to be more specific and back your position with some scientifically based facts.
Not only that - but ALL fuels in the U.S. have "additives" already in the formulation. When you say "additives", that can also mean a lot of things. Please be specific. An additive such as PTFE/teflon in your oil is always a bad thing. However, high quality fuel additives can be critical to maintaining the performance and reliability of your car.

There have been numerous independent laboratory evaluations that have shown the benefits of using high quality fuel system treatments.
These tests have demontrated a vehicles performance can actually be slightly improved by some these products due to a small increase in effective octane. This is not why you should use these products though. The true benefits of using a high quality fuel system cleaner are increased efficiency and normalized performance through the prevention and removal of deposits.

This is why I think it's very important to use a high quality fuel system cleaner. Either the type used periodically (Techron, Amsoil), or the type used every tank (Redline SI-1).

ALL U.S. fuels come with some form of additive package. In many states, the additives are combined with the fuel at the gas station. This means you may or may not be getting what's advertised.
The overall quality of a fuel is directly tied to the quality of the distillate AND the additive package. Chevron fuels have always been the best in my opinion because both the fuel and the additive package are top-notch.
However, it's still important to augment a quality fuel's additive package with supplemental cleaning over time.

Once again, Sea Foam was a good product for its day. However, I would not use it in any modern engine.

 

[QUOTE=slipstream444,Sep 7 2007, 02:12 PM] ...

Once again, Sea Foam was a good product for its day.

 

I don't see a problem with using a product Honda provides for periodic maintenance - as long as the Honda TEC is recommended for use in the S2000.
I've owned a total of 9 Hondas over the years and have never used the Honda TEC. I've always used high quality fuels and fuel additives and have never had a problem with deposits building up in my intake.
The safety in using the Honda product is the formulation is likely specifically designed, or at least tested to not harm Honda components.
SeaFoam is not so specific in design or testing. You can pick up a can of both and compare the ingredients and find they have many of the same chemicals in them (mostly light aromatic solvents). However, the magic is not just in the ingredients, but also how they're combined.

As long as the Honda TEC is recommended for use in the S2000, I think there's nothing wrong in using it - and it very well may help optimize performance.
This may be a good question to drop by the "Tell Honda" forum to see if any of the Honda bubbas can chime in on the applicability of the Honda TEC in the S2000.