I removed the cat from my 88 Esprit and noticed no significant increase in performance or sound, I dont think the 4 cyl. Esprit has a great exhaust note to begin with though. But it did smell alot worse than usual, and backfired on decelleration alot. I could have left it off because my car will be 25 yrs old which no longer requires an inspection in my state, just one time photos of the car being in good condition and sent to the DMV. I reinstalled my cat though so it doesnt backfire anymore and I think it actually gave it a little more low end that was lost when I removed the cat, I had heard something about this before that the cat makes more back pressure for low end power on a small motor.
Just for FYI
I had a 78 Trans am that I installed cats back on cause it smelled real bad upon removing them, on one occasion I almost killed by fumigation the entire line behind me at a slow Mcdonalds drive thru, on this one occasion it was killing me as well. But on this car removing the cats made it sound incredible, but its was a 6.6L.
But I had a 94 Mustang GT that I removed the cats from and it made a miraculous difference in sound and HP (at least HP by feel that is, might of been in my head), and it made not much smell at all, it had just a tiny hint of gas smell in the exhaust, of course I did this to the Mustang about 2 months after buying so it was brand new yet. What I did notice on this car was you could drive the car all night cruising and with the cats off and it almost never got real hot, you could put your hand on the intake almost always it ran so cool. With the cats on it was always real hot at least in the two months I had them on it was.
One of my first cars was a Dodge Shadow 2.2L LOL, I removed the cat from this car just to make alot of noise, and thats exactly what it did not do, made no difference at all on this car, when is the last time anyone saw a Dodge Shadow? LOL