Performance lost on aftermarket exhaust?

[rp17]

I don't know Trimmer. Sound is definately a plus. But eventhough it sounds faster, it seems like it doesn't quite pickup speed til later on at some point. Did some searches and seems like removing seconday cats helped for 986 owners. I'm in a 987 so that won't help me. Does adding a exhaust change the dyno curve?

After fitting the exhaust, me and brother travelling to a gas station. At a stop light, brother in G35 decides to take off unannounced to me, when it turned green. I had no clue, so I gave chase. (I know I know not good practice) He had a jump on me but his car kept pulling and pulling until I got to maybe 3rd gear. At that point it started gaining quickly before I shut it down. Don't know if we raced before but I've never had any other car pull on me like that pre exhaust. My car is way lighter than his too. Is this the top end gain and mid range lost? Not sure if I'm liking that.

Is this the reason why others add a tune?