You maybe running into a catalatic converter problem sometimes when converters go bad they will plug up your exaust system, and when the vehicle warms make it runn bad beacuase if air cant get out air cant come in/ no power check the air cleaner if you havent im guessing you have already, then run it up to a close to home muffer shop and have then check the converter or disconect it your self see if it helps. Make sure to post if you have anymore info id like to know so maybe i can help more.
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