I keep reading the same word about the OEM manifold when searching for high-performance replacements: "restrictive". Mainly dealing with the butterfly valves that open at 6500RPM (is that the correct engagment point?).

So what is everyone else's opinion on this matter? Are they really holding the motor back that bad (as opposed to running a manifold without this mechanism)?

 

The GSR secondaries are designed to give good low-end torque when closed, and open up in the upper RPM range to promote better flow. They're meant to be a compromise netween low end torque and high end flow. Most people that just swap a "normal" style single stage intake manifold in place of the stock GSR one with no other modifications usually see a drop in low end torque, and sometimes a drop in overall power. A single stage ITR style intake manifold will typically yield more overall power than the GSR, but it takes proper tuning(by adjusting fuel/ignition maps and using a dyno to verify results) to extract that extra power.

 

i here alot of ppl say that when the switch the gsr IM to a type r style IM that they can feel a great diff.