
I would have to say the CATZ Zeta HID system. It wasn't really a HID unit. It kept blowing out the H4 bulbs. This in turn became a costly lighting experience!
Colored bulbs that claim HID like performance, which really reduced night visibility.
Power Slot Rotors are for sure the worst rotors I've ever bought. They were 30% heavier than the factory rotors and they chewed up any pad it came in contact with it. They also loosened up the lugs on my rims (due to the slots vibrating them lose). If these rotors are used the factory torque spec are not adequate. You will need at least 95-100lbs of foot torque to keep those wheels on.
Rod Millen RMM intake system- This is one flimsy unit. It had one blot holding the assembly to the fuel filter bracket and at times it wigged forward and aft jarring loses the cone filter/ velocity stack. When the unit would move around the engine bay the filter would sometimes come close to exhaust manifold. This in turn caused the K&N filter to develop crack on the rubber cuppling to the RMM velocity stack. This is one

POS product. I ended up going back to the 3” Akimoto intake pipe with the APEXI cone filter. At least the RSA unit was stationary to the inner fender. It mounted to the existing stock air box location where it was flat and not mounted in the Y-direction (forward and aft of vehicle).
Well these are some of my bad experience with some of the after market products out there. Hopefully some of ya will learn from my mistake.
