Starts and idles perfect but when you drive it it runs about 25 miles an hour

My 2000 buick will start and idle perfect you can put it in drive and go it does real good as long as you don't floor it until it warms up about 3 miles but then it starts running horrible looses power and it will just go about 25 miles an hour you just touch the gas and it cuts out bad but let off the gas and it does perfect just when you try to give it gas what ive done to it is prior to this problem the catalac converter whent bad so I replaced it and 2 months later this problem occurred so I put a code reader on it at local shop and it said crankshaft sensor and throttlebody sensor was bad so I changed them no luck there thought catalac converter again so I cut the new converter out and it is bad test drove the car with no catalac converter at all still same problemjust don't want to keep buying parts I don't need any help will be very thankful