I have a 91 Camaro Z28 w/305. Car starts with no problem and idles fine. Problem seems to be while going down the road around 40-50 mph and give it a little gas the car seems to spudder and does not have at lot of power but when it gets past the 50 mph it runs better not great just better.
Thanks for any help...

 

is it trying to downshift...and slipping??

what happens if you just keep your foot on the throttle from below the "problem area" to past it...

 

It does not try to downshift. If I am just below the mph and give it some gas it will start to spudder and the car kind of shakes, all the way through till it gets to about 50, even then it does not seem to have the horsepower it once did, and come to think of it it seem to have happened after it had sat a couple weeks, then that is when it started to happen. I was wondering if it could be something with the exhaust? I do know that the pipes coming out from the muffler to the back of the car, at the bends are rusted out, don't know if that has anything to do with it or not. Was also wondering about the cat, if it might be plugging in some way?