Is it okay to take plain sudafed with methylpredisolne dose pack?

Too much stimulant.: I'd be concerned about the additive side effects of that combination. By different mechanisms, both Sudafed and Methylprednisolone can act as stimulants, and in combination this effect will be more prominent. If you were prescribed the steroid, I'd probably take that and not the Sudafed. Else, confer with the prescribing doctor if you feel this treatment is not helping.

Carefully, sure: Methylprednisolone is a "cortico-steroid", which some people can find stimulating, or have trouble sleeping while they are taking the pills. If you have that issue with the steroid dose pack, you may want to avoid the sudafed for a few day since it is also a stimulant, and the combination may make you feel shaky and nervous. But there is no dangerous interaction for otherwise healthy young people.