I believe you'll see a marginal increase, but not enough to even notice by removing cats, and as Beechkid stated, it's a heavy risk. I ran catless on my 85 F-150 with a built 302 and couldn't tell a difference around town or in the 1/4. The only time I've ever seen a difference was my Honda VTX 1800 motorcycle. The cats were incorporated into the muffler and were extremely restrictive. I picked up a good bit of gas mileage and power after removing them on it, but this is a totally different design than a modern sports car exhaust system. I put headers and eliminated cats on my 2001 Dodge 4x4 (that had 3 cats) due to exhaust problems, and I can't tell a lick of difference in power, and I'm still getting 11mpg with my 35" tires.
IMO, unless you're having major problems as I was with the Dodge and are exempt from inspections, don't pull the cats. Under any circumstances, I wouldn't pull them strictly for a power gain unless you're running a 1500 hp forced induction monster that may have cat failure due to flow rates, temperature, and A/F mixture. Even when I build my engine and throw on FI, I intend to keep high flow cats with my 800hp goal.