Choosing the correct valve shim replacement

I have a 1983 ltd KZ 1100. Had some backfire/afterfire issues so I figured id start with the valves. My current readings from cylinders 1-4 respectively are

Exhaust- .10 .13 .15 .13
Intake- <.04 .10 .13 <.04

The my smallest feeler was .04 and it wouldn't slide in but the buckets will still turn, so I have some clearance. Both shims under 1 & 4 are marked 250 and mic out at 2.55.

My question is, would you recommend I replace these with 2.45 or 2.40 shims?

You mentioned that both shims mic at 2.55 but are stamped 250. Are you sure your mic is calibrated properly. I would have expected that the shims would be thinner than what is stamped after wear from use rather than larger. Having said that, I recently had a very similar readings with my 1 and 4 intakes. My smallest feeler gauge was .038mm and still could not get that in. But the buckets still turned. I went down two sizes (from 255 to 245 for example or .10 smaller). So I was expecting to have a greater than .1mm clearance considering the buckets could spin. But going down .1mm on 1 and 4 intakes I ended up with .1mm clearance spot on. Which I'm fine with. Hope that helps.

They are coming out to anywhere between 2.53 and 2.55 depending on how hard i squeeze the mic. I think i'll try dropping down to 2.40 and see what measurements i get from that. Dont wanna spend the money on multiples at the time being if I didnt have to.

Do you have any smaller shims(from another valve) you could move in to measure with?

No spare shims as this is the first KZ ive owned. I had tried searching before posting, with not much luck with my situation. Just saw the post below about J motor valve adjustments, he seems to of been having similar problems. Im gonna order two 2.40 and see what kind of clearance I get with that. Thanks for the help.