There are a lot of differences between the SP1 and SP2. Many parts will easily interchange, many other parts should not be interchanged or won't easily interchange. I personally went SP2 or nothing for the improvements. For track I'd only do SP2 as the handling benefits at the limit are very helpful. Note that there are still many happy SP1 owners.
An SP2 engine will work in an SP1 but you want the header as well. It would be a shame to use the SP1 throttlebodies, but with SP2 versions you may need the airbox, maybe all the wiring harness and ECU stuff too.
Last edited by kwtoxman; 02-23-2013 at 10:22 AM.