i have attempted to tune the SR's 4A-FE and let me say that it is far easier cheaper and less soul destroying to find another powerplant, be it and old mr2 4A-GE engine or the newer levin's 20v 4A-GE, both of these are relatively painless swaps that the chassis will have no problem taking. I would not advise turboing the 4A-FE as there are more gains to be had and development potential from an engine swap (cheaper in the long run).