>Hi all
>Is tuned pipe a big plus or what?
Depends. The tuned pipe allowed people to use engines that were powerful but too unstable to reliably work. You have to remember that in the mid-late 80's there weren't any engines available that would work unmodified, since they had all been discontinued (ST46 in 1982-3, ST60 (good version) in about 1984-5).
Now, you can get a lot of reasonably stable engines that will run on a muffler, and if you are really into experimenting, a 4-stroke. These will work well to first approximation, if you follow the directions (the CORRECT directions from accomplished competition fliers- and there's a lot of utter nonsense floating around, particularly for 4-strokes). But, you get what you get.
A piped system is probably capable of better performance, assuming you know what you are looking for. They are much more adjustable, and I like and can hopefully take advantage of that capability. But, and this is important, if you can adjust it, you can adjust it wrong. I've seen a lot of people go way off the deep end of setup trying to "adjust it" and just screw themselves up. If you follow the directions, you will get a usable system, but maybe not optimum. If you get too far off the plan, it's can be a very frustrating experience.
To take full advantage of the flexibility of piped systems, you need to understand the underlying principles of stunt powerplants, be qualified and sufficiently experienced to objectively assess the results, and own and know how to use a pitch guage on your graphite props.
Having put enough caveats on it, piped systems are the de facto standard for stunt, and have been for about 15 years. 4-2 break motors are rare at the highest levels, and even their most ardent supporters have for the most part moved on. There are a lot of very good reasons for this, not just fashion, impression points, or the "lemming effect".
One really good reason is that the engines (PA and RO-Jett) are made so much better that $400 for something that will run for 5-6 years of competition flying with no problems is cheaper than trying to keep a lot of production engines on life support. I've spent roughly $1000 on engines for the last 15 years, and that's $66 a year - or about the cost of one NATs trip, or 4 gallons of fuel. I am certain I spent close to that much trying to keep ST46's alive (no mean feat).
If you aren't going to fly as much as some of the top fliers, then it's a personal decision whether it's worth it or not.
>In my RC days adding a pipe was for extra vertical
>performance
>but they also idled well and could be run on the rich side
>What setup is being used with these please?
I'm not quite sure what you are asking, Widely varied. If you want a standard system to start with, I recommend either a OS40/46VF (discontinued but there are a lot of them around) or a PA61/65. Both of these have a huge base of knowledge behind them and are known to be at least moderately forgiving of off-nominal tuning. Other engines are fine, although they are either more touchy, or too new to have a large amount of commonly available setup information.
>Are they run 4-2-4 or what?
Sometimes. The 4-2 break on a lot of these engines, combined with the pipe response, can be FAR TOO MUCH. I run the 40VF in a constant 2-stroke (boost/brake regulation provided by pipe and variation of ignition timing in the 2), and I run the PA61 in a constant 4-stroke. I run the RO-Jett across the break with no ill effects. Like I said above, you can probably make it run reasonably well in any mode if you know what you are doing.
) and RC Combat crowds. 
