chevy S-10 sounds good but takes forever to go on 1994 Ford Thunderbird

we changed from a 2.2 to a 4.3 in a chevy S-10 it sounds good idling but when you go to drive it it takes forever to git up to 50mph or higher what could the problem be?

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1 answer
What else was changed besides the engine! Had to change the ECM. What else? What year is this S 10 truck?