I just recently replaced my stock intake manifold with an Edelbrock Performer and gained 15rwhp/7rwtq on the dyno. The job isn't difficult but be prepared to replace some old plastic/rubber vacuum lines in the process. I'll try to walk you through it as best as I can:
1. Disconnect the negative battery terminal.
2. Drain the cooling system completely.
3. Loosen the clamp holding the airpipe to the throttle body and remove the air filter housing with MAF and airpipe as a complete unit. Disconnect the wiring to the ACT sensor and MAF from the main harness.
4. Disconnect the wiring harness connectors from the TPS and IAC, disconnect the throttle and cruise cables from the throttle body, and unbolt the EGR pipe from the upper manifold elbow.
5. Disconnect vacuum hoses from the EGR, smog pump, and fuel pressure regulator.
6. Remove Torx screws holding emblem plate to upper manifold and remove all 6 upper to lower manifold bolts.
7. Carefully lift the upper manifold with throttle body away from the lower manifold and disconnect vacuum hoses from underneath. These rubber hoses may be hard and brittle so be prepared to replace them.
8. Disconnect the upper radiator hose, water pump bypass hose, and the heater hoses from the lower manifold.
9. Release the fuel pressure from the Schrader valve and disconnect the fuel lines from the fuel rail using a special disconnect tool.
10. Unplug the ECT sensor, coolant temp. gauge sending unit, and injectors to release the wiring harness, and disconnect the PCV valve from the back of the manifold.
11. Remove all the bolts holding the lower manifold to the heads and carefully lift out the manifold with injectors and fuel rail still attached.
12. Clean up any coolant that may have spilt into the lifter valley and begin to scrape away all traces of gasket residue and sealant from the head mating surfaces and block. It would be a good idea to temporarily stuff large pieces of clean shop rags into the intake ports to prevent gasket material from entering the engine.
13. Transfer the thermostat housing, thermostat, heater tube assembly, injectors, and fuel rail with regulator to the new lower manifold. Use new injector o-rings and lightly coat them with Vaseline as you install them.
14. Apply a thin coat of RTV silicone to the lower manifold gaskets and set them in place on the heads.
15. Apply a thicker coat of RTV silicone to the manifold-to-block mating surfaces (do not use rubber end seals).
16. Carefully set the new lower manifold in place ensuring that you don't move the gaskets from the heads, and bolt it on to a torque of 25lbft.
17. Reconnect the PCV valve, fuel lines, injector harnesses, and connectors to temp. gauge sending unit and ECT sensor.
18. Reconnect the heater hoses, water pump bypass hose, and upper radiator hose.
19. Transfer the PCV vacuum hose and fitting from the old upper manifold to the new one.
20. Reinstall the upper manifold with throttle body. Make sure that you reconnect vacuum hoses to the underside and carefully align the upper to lower manifold gasket. Torque the bolts down to 25lbft.
21. Reconnect vacuum hoses and fittings to the throttle body and intake adapter elbow.
22. Reconnect throttle cable, cruise cable, EGR pipe, and TPS/IAC connectors.
23. Reinstall the air intake/MAF assembly and reconnect the ACT/MAF wiring assembly to the main harness.
24. Refill the cooling system but leave the radiator cap off.
25. Reconnect the battery and cross your fingers.
26. Start the engine, let it idle, and pour more coolant into the radiator until it reaches the top and stops bubbling.
27. Check for coolant, oil, and fuel leaks.
28. Go for a gentle 15-minute test drive to make sure the engine runs smoothly and there are no driveability issues.
29. Check again for coolant, oil, and fuel leaks.
30. Add coolant to the expansion reservoir until it's at the "maximum hot" line.
2006 GT - 5MT - 12.8 @ 108 - 306rwhp 324rwtq (E)