An analysis of the in situ adaptive tabulation (ISAT) speedup factor is conducted to reveal the important parameters in determining performance. The retrieval ratio was found to play the most critical role in influencing the speedup factor of ISAT. A modified search algorithm for binary search trees is proposed to enhance the success of the retrieval process. Numerical simulations with the modified algorithm demonstrate a several-fold increase in ISAT speedup factor when the retrieval ratio is high.