Swaping injectors is okay. If the problem is still there first a check of the valve clearances then a compression check of that cylinder is indicated if the valves for that cylinder were not tight. Remember I said a quick check. No reason to adjust them if the need is not there.

Try to keep in mind that many owners of long standing did not know or ignored the concept of checking the valve clearances for endless miles. Mercedes wanted it done every 15k. This attitude that a diesel engine requires no service is held by many yet is false.