Racers Edge - The baffle on the XRL is the least of it's problems. The internal perf core has smaller holes and allows less air thru than the XR.
The baffle will allow a tiny bit more air thru, but nothing like a different muffler -- plus rejetting the carb. Of course, for someone used to Briggs power, maybe the baffle removal will feel like an awesome increase :p
As far as different exhaust systems for the XR, the 1997 and later models have excellent stock systems and a baffle change (al-la Thumper Racing's insert) are all they need, unless the engine is modified, then a different muffler is called for.
The 1996 and earlier XR's need a different exhaust system. If you can find a complete system with new headers, it's the way to go -- unless it's a Cobra or DG. They don't work as well as the stock system on the XR. I've tried the White Brothers Racing system, The Supertrapp, and the system offered by Thumper, and all worked very well. Gave the bike about a 15% increase over stock hp (after rejetting).