Is backpressure causing this? (VG33E)

[213ad]

Hello, I own a 2000 pathfinder with the VG33E engine.

A couple days Ago I had my exhaust disconnected after the flex couplings (was replacing those due to rust), which left only the cats/downpipe and a short open piece of pipe as my exhaust (the muffler/resonator weren't connected).

I drove like this for a short while to get some parts to finish the repair, and aside from bieng loud as hell, I noticed a severe loss of low end torque, I was flooring it and not going anywhere. (probably took over 10 seconds just to get to 40K/PH).

As soon as I put the exhaust back together with the new flex couplings, everything went back to normal, no codes ever showed up on the OBD2.

I was considering to make it straightpiped, but with that kind of power loss it is not worth it. Do these engines just not like free flowing exhaust? or is something else causing that power loss?

Thanks for your help.