Back in 1982 Cycle Guide Magazine published an article were they dyno tested all of the early 1980's 4 into 1 pipes on your GS1100E. The Cycle Guide testers evaluated pipes from Kerker, Jardine, V&H, Bassani, Supertrapp, Yoshimura, MAC, RC etc to name a few. The article also looked at centerstand & oil filter retention.
The dyno tests were performed on a stock 1982 GS1100E and were strictly
limited to replacing the stock exhaust system with the aftermarket 4 into 1 (
No Jetting changes using stock airbox). There was only one manufacturer which made more HP than the stock Suzuki GS1100E and that was the Supertrapp 4 into 1,....QUOTE]
What was the value of this "test"?

Pretty obviously, the stock bike would perform poorly with a free-flowing aftermarket exhaust system, without the appropriate jetting changes. The real test, IMHO, would have been to compare all of the systems performing at the optimum A/F ratio. The Supertrapp performed the best under the magazine's conditions, perhaps due to the extra flexibility it allowed with tuning the level of restriction in the canister. Lest we forget, the stock system also weighs a good 30 lbs more than the typical 4x1, so even if hp were equal, the modded bike would still have the advantage, so to speak.
Tony.