98 Hyundai check engine light?

I have had my car in the shop for two months now after getting the head replace, all belts, hoses, starter, etc. The garage occasionally gets the check engine light with code misfire cylinder one. The garage has adjusted all that they can and been trying different things. They swapped the plugs with 1 and 4, error remained on cylinder one. They put a new starter on and while it did start stronger the code remained. Now they are going to check the coil. Any other ideas?
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