my 2000 buick regal is acting a little sluggish around 35 to 40 it studders a little change out fuel filter and air filter what should i do next.

Welcome to AF.

What do you mean by sluggish at 35 - 40? Is that under light, moderate or heavy acceleration, cruising?

What is your current mileage. How old are the spark plugs and ignition wires?

moderate driving i have 125,000 miles on my regal and just bought the car and dont know how long the spark plugs been in there should i start there frist

It is the best starting point since secondary ignition issues can cause a similar issue. The other possibility is the autotransaxle torque converter TCC lock/ unlock function which could cause the fishbite/chuggle effect.

Best way to tell how old the spark plugs and ignition wires are is to look at the identification markings on the plugs and wires. For wires if you see the GM Packard markings and the cylinder numbers on the wires then they are the original (OE). The OE plugs from the factory were the AC Delco 41-921 double platinum.

were is the autotranaxle converter located and is it hard to change out

I don' think anyone is suggesting you replace the torque converter, that is a major job! If you do the wires & plugs and that does not restore power, suspect a clogged catalytic converter. BTW, do you have any DTC's/CEL's (Diagnostic Trouble Codes)?

np codes but i am going to change out the plugs tomorrow so we will see whats up

np codes but i am going to change out the plugs tomorrow so we will see whats upFollow the suggestions above, if the wires look original, replace them! Good Luck!