Worth going from 18's to 17's for better performance?

[Jeff Knock]

Hi, I recently bought a 2005 z4 2.5 and changed out the 17" fan looking rims to 18 inch ZHP and noticed the car drive a little sluggish what’s the real weight difference do you guys think between the ZHP wheels versus the stock 17's looking ugly wheels?
Thinking of going back to 17" as I don't want to compromise any performance issues. Anyone know what the stock fan looking wheels weight on each???

ZHP Wheels
18X8 F, et47, 27.78 lb
18.85 R et50, 28.72 lb

(updates)
Basically this weekend I dropped by 20's to 19's on my F80 m3 and shaved off 17.5 lbs around and my car flyyyyyys now, so I started to look into my Z4 and do the same as I have the 2.5 and upgraded from 17's wheels to 18's and wider rear tires, I love the look of the ZHP but performance I will not sacrifice (graah). So why I am asking this 😉

[XMetal]

Besides wheels, look into what tires you have. Different tires have different weight. You can save 2 to 6 lbs per tire alone if you look hard enough. Are you still using run-flats on your 18" setup? Run-flats are usually heavier than conventional tires.

[Jeff Knock]

no, i got nitto motivo season/performance and I am considering Sportlines csl or apex Arc 8 they are like 19 to 20'b ea vs my ZHP 26 to 27lb ea which is madness