I own 2 Colts and 2 HK 45's. I believe it is worth noting that the Army's shooting team uses STI. With S&H costing as much as $65 each way, its often worthwhile to buy it exactly the way you want it.
I've invested in a custom fitted bushing and one piece guide rod. Improved accuracy but now I need bushing wrench & a tremendous amt of energy to take apart. Plug comes out at Mach III and if your not prepared for it, you'll never find it. ( I keep a spare JIC