get a lexmaul 4-2-1 outlet manifold. dibilas inlet manifold if you want to pay an extortionate price
1.8 - Z18XE comes with software giving gains of 22ps.
1.8 turbo is possible i believe dilibas now do a kit, althougfh i think it will be cheaper and more profitable if you want serious power to replace the engine. a let lump will set u back around 1700 and the turbo kit will be the same. installation will be both as pricy as each other due to the fact they are engine out mods.
DBILAS DYNAMIC TURBO SYSTEMS Astra G Z18xe 230 Bhp
Description The systems include full kits: Flowtec Manifold, Turbocharger, Dbilas Exhaust Manifold, Intercooler, Flowmaster Air Filter and Flowpipe, Exhaust Downpipe. All Intercooler Pipes with Hoses, Oil and Coolant Lines, Software to suit the application PriceŁ3,902.68