ABSOLUTELY NO REASON FOR THE TB. A non boosted spi is slow, there is no getting around it!! you will not feel even a 5 whp difference, ur butt dyno can't tell, and in the long run, for accelleration, that's all that counts. The only reason you should go w/ a TB is for throttle response, and you may feel it there, but w/o any other real mods, and on the spi, I am referring to boost, it won't benefit you!! The suspension is something you will be able to FEEL in every corner, just taking it a little faster than b4 gives you more lateral g's. and that you can actually feel!! as for the parts beeing rare, who gives a flying flip!!! if it does you no real good, then what is the purpose??? The spi will not make huge power unless turbo'd, not even on an all out NA build, you'd b lucky to hit the same hp as a simply bolton zetec, so, unless you KNOW u are boosting ur car, go w/ the suspension, ur car will feel like a whole different animal!! else, you will be wasting 200 bucks IMO
*you will also want softer tires too!!