does it make a difference....

[peoriasky]

I am only doing two mods to my redline. The GMPP stage kit/tune and a HF cat. Will it make a difference which I do first? If i get the tune on and then install the cat will that cause me to throw codes? I freakin hate CEL's.

[TomatoSoup]

It should be fine if you do the cat first. You'll get a boost of energy for a while until the ECM learns down.

Two other mods you MUST do (unless your car already has them) are the DDM backbone and probeam. TRANSFORMS the car's handling (and safety in the corners), especially with more power.

[Rob the Elder]

What's left to say ...

The DDM Probeam is so good, I recommend it as the first mod.

If you install the HF cat without the GMPP kit, you will get more sound but no lasting performance increase. If you later install the GMPP as Soup stated, the new software parameters will allow the HF cat to increase torque and power. In essence, the ECM will "learn up". To the potential of the cat. I did it that way.

[miller11386]

Probeam and backbone are my favorites. WR is a good idea too