Toyota Repair: car performance, toyota tercel, carburated

Question
My Toyota tercel wagon 1987 3A-C carburated. auto, is too sloww starts quick do n ot hesitates,do not missfires nor backfires,transmission runs good mean do not slips and switches gears o.k ,but I can't go faster than 40 miles /h, changed plugs,set rpm's, what is wrong?.
Thank you
Joe

Answer
Check for a clogged exhaust system or possible catalityc converter that is plugged up, disconnect the exhaust pipe just in front of the converter and drive the car to see if there is an improvement, if there is replace the catalityc converter and the muffler.