Let's get to the meat of your question and leave the homemade tattoos for another day shall we? I was actually contemplating going to a straight pipe myself not too long ago but have since held off because I know the noise without a cat will be unbearable. My friend's S70 T5 has no cat but he has 2 mufflers AND a modest sized straight through silencer to combat the extra drone and noise. The cat acts as a very good silencer. Plus, his check engine light is constantly lit. He doesn't mind although somehow I don't think the ECU knows what to do with the reduced restriction because it wasn't programmed with a cat bypass code in the first place. Running with a constant check engine light isn't necessarily disastrous but it may mean that your ECU is not getting the fuel/air mixture right and this can actually decrease performance. Unless you're getting a custom ECU that has been programmed with the right fuel maps to accomodate a car with no cat present then it may not be such a good idea to run without it.