what can cause loss of power?

95 Rodeo 3.2L

I know there are probably a lot of answers to this question but my Rodeo is making a lot of hissing noise underneath when hitting the gas - also sounds like I don't even have a muffler - loud exhaust (actually loud even at idle). Probably a hole in the exhaust pipe after all these years of road salt, etc. - I can hear the noise echo off barriers and other cars as I drive by. Is this alone enough to cause loss of power?

I hit the accelerator like I used to but it's just not getting the same pick-up... takes forever to even get to 40mph from a red light if you know what I mean. Could another part underneath be damaged - catalytic converter contribute to power? What happens if an O2 sensor goes out on these things - will there be a warning light?

Sounds like it could be something to do with the exhaust manifold. Engines need backpressure which helps low RPM torque. Probably not the O2 sensor unless the power seems more normal from a cold start. O2 sensors have to be hot before they work correctly so the PCM ignores it until it starts getting a proper signal. If it had normal performance but dropped once the engine got up to temp then I would suspect the O2 sensor.