I have about 10,000 miles on my SC. So far reliability has been pretty good.
As for the returnless fuel system, how are you planning on increasing the fuel pressure and flwo rate to the larger injectors without running into problems with the smart pump? a chip is a start, but a chip can only do so much... not to mention Vortech refuses to custom burns, so you are going end up spending an additional $125 to get it custom burnt for your setup. Then you might run the risk of having it not work.
Check your fuel system...
-Mark