I got a 99 EM1 riding on stock suspension setup and i'm looking forward to upgrading with Koni Yellow soon, but i don't know which coil over system works best for those Koni Yellow. Is all coil over system the same? What about Ebay coil over systems? Are they any good? If so, which system should i go for?

 

You need Koni specific thread sleeves.

Ground Control or Koni makes these thread sleeves. Idk if anyone else does.

You cannot safely use eBay coil sleeves on top of Koni Yellow shocks.

Additional info: Don't plan on lowering the car more than ~1.25"-1.38", unless you don't care about ride quality.

 

So its sounds like i should go with the Koni Yellow and Ground Control combo then. What about the sleeves? I mean, doesn't it comes with the Koni Yellow for my specific specification?

 

The thread sleeve is part of the coilover conversion...not the shock.

Koni yellows come with mounting C-clips that can support either the supplied spring perch for stock springs or lowering springs.....or can support a (not supplied) sleeve for a coilover conversion.

GC's will come with thread sleeves. You use those thread sleeves DIRECTLY on top of the C-clip. Make 100% sure they are oriented correctly.