without custom fabrication there isnt a whole lot to be done to the SPI, but I personally love this engine. I have about 110k on it, and it still drives great. If you want a little more fun out of it you can do I/H/E with some gasket matching on the intake mani and exhaust manifold/header you will need to have a custom flange made (but if you have good friends, you can have someone made for cheap!!! my buddy is a machineist and he will make a stainless flange for about 30 for me.) And after all that you could look for a TB 65mm or bigger, then top it off with a tune...anything past that its all $$$$$ for boost. Currently my build is on hold, and i am continuing the build started by jrdyfocus84 ( look him up and read his once build thread) i plan on having it done by mayish of next year. Without boost on a N/A build, without serious engine upgrades, and a custom cam, in the area of 250hp and 230ish lbs of torque is the top end with everything else done, now that would be a ton of fun, but i always want to push it. Im finishing this build that he started, and looking for 300whp and torque as a baseline, based off what he has and what i plan on doing...im trying for 450whp and up, just so I get to laugh at my brother when a ford focus FWD sedan, beasts his 3.7l v6 2012 mustang with cams, adj gears, borla exhaust, long tube headers, and an aluminum 1 piece drive shaft.
2 12" rockford fosgate subs,1500w Hifonics amp, throttle spacer,Escort Header and cat delete with FSWerks 2.5" race exhaust,custom CAI w/Spectre 10.5x6 filter,smoked tails,Euro turn signals, 30,000K HID headlights, Toms Tune