could be a few things.first check to see if all the clamps are screwed tight on the black tube between the air filter and the engines intake/throttle bodyy.also make sure there are no cracks or holes on it.the reason for this is all the air that goes to the engine has to be measured to accurately give the correct amount of fuel mix to your engine.if this tube can be wiggled or slightly moved it is leaking and air being sucked in at this leak or leaks has not been measured through the tube so the computer in not setting the mix of fuel correct..this is one of the causes of chugging that is very easy to eliminate for free with the aid of a flat blade screwdriver and orflex ablee tape such as black electrical tape (a buck or two at any parts store) if your tube is leaking from a cracked/split or dry rotted air tube due to the age of your auto.another cause to check for free is to open your hood at night in the dark to see if your spark plug wires are bad (you will see and hear them sparking to nearby metal such as a flint ofcigarettette lighter arks) cautiodon'tont touch them because they wiZAPapp you with a strong jolt of electricity (shock you like a taser).Good luck/hope these "try frsuggestionsons fix it. there are other possible causes but they would need to addressedsed by someone who is qualified to look at and eliminate,tune up,check for fouled plugs,oconsumptionion,etc.
