You don't "need" to use IGF while taking GH, but you are still going to need to use an insulin pin to inject your growth. IGF can be a great addition to a GH cycle, elevating IGF levels just that much further, but it isn' necessary to make progress. Much of the results you get are going to be based off of dose and duration of use. If growing muscle is your main goal, IGF would help. If you are trying to get lean, it will still help retain muscle, and increase pumps, but it won't help so much with fat loss.