TechT bolt engine is really nice and so is the APE board, I would suggest a nice barrel kit as well. A new trigger is personal preference.
MacDev Militia: Clone GTi with Shift Kit, GTi Valve, Pooty Bolt, & Violent Series Trigger
dp Fusion FX with TechT HUSH Bolt & TechT LAW RAM
Disruptive Balance Barrel, Sly Pro-Merc Diesel Barrel Kit, dye Rotor with Exalt Speed Feed, & Crossfire SS HPA 68/4500 Tank.