Try this:
SET @ImpactIntakeID =
(SELECT STUFF ((SELECT ',' + CAST([IMPCT_INTAKE_ID] AS VARCHAR) FROM [IMPCT_INTAKE_REQ]
WHERE [CNSDR_PROJ_ID] IN (SELECT Proj_ID FROM PROJECT WHERE YEAR(Enter_Dt) < (YEAR(GETDATE()-7))) FOR XML PATH('')), 1, 1, '')
AS ImpactIntakeID)
OR
SET @ImpactIntakeID =
(SELECT STUFF ((SELECT ',' + CAST([IMPCT_INTAKE_ID] AS VARCHAR) FROM [IMPCT_INTAKE_REQ]
WHERE ',' + @ProjectID + ',' LIKE '%,' + CONVERT(VARCHAR(20), [CNSDR_PROJ_ID]) + ',%' FOR XML PATH('')), 1, 1, '')
AS ImpactIntakeID)