Sounds like a bad cat. When they plug up or go bad they get very restrictive and power goes way down. I had one so bad I couldn't go over 35mph. Turned out the O2 sensor went bad and the engine ran rich and screwed up the cat.
a clogged cat cause my engine to go at 16k . i had no signs beforehand. the car would run fine at regular driving but as soon as you floored it the car would click and die out,. it would also take out the driver info center and would not let a snap on scanner communicate. it took about 2 minutes to get the vehicle started after it died.
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