A set of high-tension valve springs for all VW 4-cylinder 16v engines, these will fit your 1.8 KR/PL-code head or your 2.0l 9A or ABF. The benefits are the same. -means to REV and make big air flow.
Springs do not work along, of course. Go with lighter but stronger 16V Titanium Valve Retainers, too.
Combine these tuning "weapons" with 16v Lightweight Lifter "ammunition" for serious motorsport "firepower". This is the winning combination for hardcore builders.