So today I finally took the time to install a few parts on my 03 Z that have been sittin around in my garage for awhile now..

I installed the Motordyne 5/16 Iso Thermal Plenum Spacer, Injen CAI, Helix Power Tower Plus TB Spacer, and HKS Rep True dual exhaust. I have the UpRev Standard but didnt have the time to flash the ECU today so will get to it tomorrow.

Overall I am very happy with these products. Everything was a fairly easy install, with very little problems. I know the HKS Replica has given people a few issues, but with minor modifications the fit is almost near perfect. The only problem I am having is when I took the car for a little test drive, when WOT the exhaust sounds great! Or when reving up in neutral it sounds bada**! But when I let off the throttle and as the car idles down, it is making a god awful rattling noise (like metal clanking). It seems like the car is having trouble idling down and almost feels like its stopped up or choking. The car is so small that I can not tell if it is coming from the front or rear. Does the ECU still need a little more time to adjust? Or is this just from the sh**y exhaust I just purchased? Could flashing the ECU possibly fix this?

Also installing the plenum spacer required me to remove the strut bar. When I swerve or make a fast turn there is a terrible grinding noise. Should I torque it down a little?

Yes I know HKS Reps are usually sh** but I decided to give it a shot.

Any opinions or help will be greatly appreciated!

Thanks,
CB

 

Are you sure it isnt a clearance issue. Ya know the exhaust just banging up against something underneath you car. Just a my thought with the (like metal clanking) sound.

 

It's pretty common to have clearance issues with the plenum and strut bar. If you tighten the strut bar too much to give more clearance to the plenum, you can easily push it up and it rattles against the hood. If you don't crank it up enough, the plenum will strike the strut bar.

You're gonna have to experiment to figure out if where contact is being made. Get some foam tape and put it on top the strutbar and see if that quiets it down, if it does then you know the strut bar is too high. If it doesn't try the tape under the strut bar to verify it's the plenum rubbing that making the noise.

 

I thought this too, so double checked fitment and it's bolted up pretty tight. I made a few modifications with U bolts to secure it better and it's definitely not that.

 

I will check this for sure. But the rattling is only when I let off throttle. Not when throttle is engaged so that makes me think its the exhaust. But the grinding when turning could be from the strut bar. I will mess with it tomorrow and see.

 

The rattling could be from one of the pipes rubbing against the subframe (this was my case with a different exhaust). Check that nothing is rubbing.

 

My HKS replica exhaust canisters were hitting one of the diff nuts so I had rattling as well

 

Yes! This was the problem. Must've missed it, it was in a spot that I couldn't see so I ran my hand across the top of the pipes and found metal shavings which lead to the diff nuts. Fixed it though, so I am satisfied now with this exhaust. Thanks for your help.