I recently had a new used engine (64,000 miles) put into my 1999 Corolla. Before I sent it in, it ran great with the exception of heavy knocking above 2500 RPMs (some intelligent individual wanted to wait till payday to put oil in his car). Literally ran almost perfect. It sat for 3-4 months before I sent it in to get the engine replaced. Driving the car to the shop, it ran just like it had before - nothing unusual. But When I got the car back, the engine was VERY boggy until the RPMs hit a certain point (imagine your grandma driving an i-3 metro.) Once the RPMs/gas pedal hit the "takeoff" point, the car moves like a bat out of you-know-where. I'm assuming this is around 3,000-3,500 RPMs, but I'm not positive because my car doesn't have a Tachometer. So my car is either accelerating very slowly or incredibly quickly depending on the RPMs.
The engine I bought did not have a throttle body; this was transferred from my old engine, so could be part of the problem? My mechanic told me I should run premium fuel in it and clean out the used engine, but I do not want to spend $3.30/gal on gas. And More Importantly, it doesn't seem to be helping. This problem could be dangerous once the next snow falls, so I want to get it fixed as soon as possible. It has to have been something related to the installation of the new engine, but I'm clueless as to what it could be.