WHAT COULD BE THE REASON FOR LOST ACCELERATION

You must go into much more detail than that. Specifically what happens, when it happens, what you see or hear. What you have done, like servicing recently. As it is now your question is not answerable. So try again.

What year is it. the ECM has a defect in the 2001 - 2004 Toyota extended the warantee on the 2001 - 2003 but most are out of warrantee. It acts like it is pulling too heavy of a load then slams into gear. if that is happening to you then I sugest you send it to Brooklyn NY that's what I did and my car runs great now.