From the one timing map I've seen, the L05 (no idea what application that map was) may actually hinder an L31 because it's tune is so conservative. It's not all about timing of course, fuel requirement to feed 50 more HP is not insignificant and is not something TBI can adjust for.
L31 has to have an external EGR run to be legal. Last I looked at the kit, it was pretty pricey, and I'm not sure what you'd do without headers, since it requires welding a bung to the exhaust. I ran one for quite awhile, but ditched it. Partially because I saw zero benefit to running it, and also because it ran over the valve cover and made access a pain.