This made my car sound like ass and be wicked slow off the line, don’t ever remove the rear muffler from a 16v car. The reason why I tried is because on my turbo car it sounded the same afterwards and was faster. A week later I put back on the stock muffler minus that stupid Volvo S bend at the end of the exhaust. The car is much happier being muffled. Recently I bought a welder. My exhaust is dying including the cat so in the spring I’m going to buy a Volvo replacement muffler system including cat for this car. At that time I will redo this experiment and also make up a pipe to bypass the center muffler, but I don’t expect it to end well.
If you remove the muffler as you call it we call it (the silencer in the UK) it will not perform correct because you will lower the back pressure so upsetting the air flow through the engine. There needs to be some resistance in the air flow with out it all mixtures will be wrong IE no power