Clogged exhaust?

[chicklin]

'86 K10 Suburban, 350, 700R4, stock catalytic converter and muffler.

So, I've been getting the motor on my new/old Suburban tuned up and I think I've got it dialed in pretty close. I'm pretty sure I still have a vacuum leak somewhere b/c it idles high (i.e. I had to set it rich on the idle mixture to make it idle smooth which then made it idle high).

Anyway, the other issue I'm now having is that I seem to have lost all my power, particularly in the mid-to-upper RPMS ranges, like when I've driving on the interstate.

The engine runs smoothly now, no misses, vibrations or noises, but I've basically got to floor it to get it up to and maintain highway speeds. The timing is set to 8 btdc per the sticker, so I don't think that's the issue. Even if it was too far retarded, that would generally just affect acceleration, not holding it at speed, right?

The other thing I noticed is that, with the window down and giving it some gas, I can hear the exhaust "spitting". It kind of sounds like when you have a miss in the ignition, but the engine is not missing. Could this be from the exhaust being restricted, pressure builds up and it finally blows through and makes kind of a "pooof" noise?

If it is the cat, is there a home remedy for this? Once, years ago, I had a truck with a similar problem and drilled several holes in the cat. I can't remember if it helped or not, though