Catalytic Conveter Diagnosis HELP!

[Fortress]

I tried a couple rounds of techron, and reluctantly tried CataClean, which is suppose to help cats and fuel injectors. No dice on both as expected.

I'm thinking up all night is into something with the rail pressure check. My lemur scanner from Bav auto also doesn't do rear fuel trims, as it's a closed system, but the voltages seems ok all around. One thing I do notice is that getting on the gas the manifolds sound a little louder than they should, and if I let off the gas at hwy speed the car does feel like there's almost some back pressure. (Then again I have no reference as the cars new to me.) thoughts?

Indi says try a rear bank 2 02 sensor but I think that's a waste given the voltage is ok.
I just stopped in at Bav auto tonight and picked up a fuel filter ( I always change that w any new (used) car I get, and a gas cap, as mine doesn't seem to have much vacuum. I'll s**t if it's the dam gas cap...

I haven't looked yet but will research fuel pressure and I assume there's not a diy on checking at the rail.

Keep you all posted and thanks very much for the help! Have a great thanksgiving. Off to change a fuel filter...