If the problem in fact only exists in the front cylinder, perhaps the front boot/clamp aren't fully seated or tight enough. Another idea is maybe the injector o-ring isn't sealing well or is too hardened to seal well or was pinched a bit on install after the injectors were cleaned. Hot usually means lean, so those two ideas represent ways that air could be sneaking into the front cylinder. If the injectors were thoroughly cleaned I suppose that eliminates a semi clogged or poorly working injector. Lastly I am not sure if too-tight of valve clearance could cause heat issues, but maybe that's possible as well.