I had the exhaust tailpipes removed from the catbacks on my ITR Mustang, in part to reduce weight. In their places now are "turndowns."

The exhaust tailpipes extended from the mufflers, which are located just ahead of the axle, to the very back of the car, snaking around the axle and panhard bar bracket. As such these are long pieces.

My question: What usually would be the change to the backpressure? Would it be anything significant? I hope I don't have to revisit a tuner to reset things.

Thanks for any replies.