This car isn't really torque starved imo. The HP on the top end is the huge issue. Ford Performance knew that and if they can achieve the claimed numbers that's a huge jump.
$800-1000 for a catback exhaust...... or $150-175 for muffler delete. The sound note is not much different. If anything its deeper with muffler delete and you save $500-800 to spend on parts that actually matter like an intercooler.
Can you please post pictures of where you applied adhesive tape. I've been looking for a fix to this, I know the C Pillar piece your talking about just would like to know where you applied the tape in a picture :).
They are still working on it though. It'll come this stuff just takes time Ford Performance has many projects they are working on and since this was 50 state legal. In a time when companies are cheating emissions I'm sure there were some delays getting this CARB approved.