3.4 not running right

96 GTP, 3.4L. at idle, engine is slightly rough, rpms surge a little. at ~35 mph, the motor starts missing badly until speed is increased. when sitting still and starting to accelerate, the engine bogs down. can push pedal down and nothing until it decides to pick up and go. had timing belt replaced and dealer says cam timing is correct. getting dangerous to drive, dealer has had car 2X and can't find anything. no code in computer. any suggestions? want to add, the maf and idle control valve were replaced, new plugs and wires, ac/delcos. cat clogged maybe?

Bad TPS, bad fuel pump or blocked cat. Check the throttle position sensor and if it checks out ok then check the cat. There is a test procedure listed on how to do it. If the cat checks out then the problem may be in the fuel system. Check the fuel pressure at the regulator if it is low, less than 40 psi at idle then replace the fuel pump.

Here is the thread with the cat check procedure:

http://www.automotiveforums.com/vbulletin/showthread.php?t=440952

thanks for the reply. we will check the cat this week. problem is getting worse, so mechanic should be able to find the problem soon.