As Marc said, OBDII is an emissions spec, and the emissions test is done via the port below the steering wheel. I do use HPTuners to tune my car, and had my tune pass the OBDII port emissions test here in Albuquerque, NM. It's our first year doing this type of testing, and didn't even know it was coming, so I was a little worried when I had to get my smog test done. I shouldn't have worried at all! If I knew that all they could see was what I've already been looking at on my laptop for the past couple of months, I would've known I'd blow thru that test. I even had my EGR turned off, which I think is supposed to be cause for failure, but since it didn't throw a code, I was okay.
As far as emissions go, a well tuned (for power) car usually has clean emissions. That's explains why I've heard of Ultima GTRs running LS1 engines in California without cats, and exemptions of course, but still passing the sniffer test with flying colors.
Back to HPTuners. Yes, surely they've made advances since '96, but I'm probably not smart enough to explain it properly. The biggest change is a technology shift in memory types. Older memory types had to be exposed to UV light, others had to be placed in special memory writing sockets, and most of those had a short lifespan if constantly rewritten. I'm not sure what type of memory is being used now, but at least it allows us to rewrite the code on the chip without removing it from the vehicle, or even turning a single screw.
While I use HPTuners, I still think programs like LS1Edit are okay, even though not as great of a value. For one thing, I can analyze any GM OBDII vehicle, and reprogram any '98 Vette. This means if you know someone locally with the same model and year vehicle, you could share a single copy of HPTuners. LS1Edit is locked into one VIN--no sharing.
HPTuners should be available for the 04 SSR, and if it's not, it will be soon.
I can't tell you what kind of gains to expect since it really depends on the skill of the person tuning your vehicle. At one point, my butt dyno was telling me I might be down 30 hp because of my lousy programming skills. Now I think I'm at least back to stock power, but I'm not sure yet. One of these days I'll go visit a dyno and find out for sure. The one thing I am sure about is that the further you mod, the greater the benefit you'll see from properly reprogramming your vehicle.
Well, the question to answer is: Is it worth it? Well, if you would like to drop some weight and gain a little power by removing the EGR and AIR systems, you'll need a real programmer like HPTuners or LS1Edit. If you'd like to optimize your fuel economy and power levels, you'll need a real programmer. If you'd like to "see" if your knock sensors are picking up anything, because they are, and how much spark is being pulled, you'll need an analyzer, like the one that comes with HPTuners, or a standalone analyzer-only program like EFI-LIVE or EASE. If you want to make the most of aftermarket headers, intake manifolds, intakes, spark plugs, and especially internal mods, you'll need a real programmer. I've heard claims of 15 more horsepower AND an additional 2 mpg highway on a stock motor from good tuning. A good programmer and analyzer can help you notice and thus correct problems that would otherwise shorten the life of your engine.
Here are the choices:
1. Let the stock program try to figure it out
2. Take it to a tuner and let them tune it
3. Buy a handheld tuner and press the optimize button
4. Buy a real programmer and learn how to do it yourself
Pro and cons:
1. It's the cheapest option, but the stock program can only adapt to soo much, and was never optimized, even for the stock components. It may work for a while, but big mods will eventually exceed the flexibility of the stock program, and codes will be throw.
2. It costs $500 each time, but it's a professional tune each time. I buy parts one at a time, so the intake, air bridge, coupler, intake manifold, spark plugs, headers, cat back would've cost me $3500 in tuning if I brought it to a tuner each time.
3. It's easy, and a little cheaper than a full fledged programmer. Problem is it's limited, and makes changes without checking beforehand to see if they should be done, and doesn't check afterwards to see how the changes are working out. It's also extremely limited in what can be changed.
4. It's capable of changing almost any parameter you could think of...definitely more than I'm capable of wrapping my mind around! Detailed changes can be made to tune your engine down to the finest detail, thus fully taking advantage of the benefits of electronic fuel injection. Analyzers like the one that comes with HPtuners can check to see if anything needs to get done, where optimization or repair should be made, and can check to see the results afterwards. The new version of HPTuners can utilize a wideband o2 sensor, so trips to the dyno aren't really necessary anymore, so that saves another $25-$50 per dyno run, which would probably cost me $75 a weekend if I used the dyno when I tuned. The tough part about full fledged programmers is that it costs $500 to get on board. To do it right, you'll want a laptop to analyze the vehicle while you're driving. To really do it right, you'll want to also buy a wideband o2 sensor ($350) to tune for wide-open-throttle.
Well, good questions! Let me know if there's more I can help you understand.
Eugene