I'm getting ready to tune my Fiesta with a flash tune from Dizzy for both 93 octane and E30. I have all the parts that I need except for a DV, which I'm undecided on. From what I understand, an upgraded DV would help with consistent boost levels, especially with a tune. I have no experience with tuning though, so I don't know how exaggerated any of these claims are. Is a DV necessary to have for a tune, or even that helpful? I just want to be sure I'm not wasting money on unnecessary upgrades, especially when an AP, spark plugs, the tune, smoke testing, and tools are already getting quite expensive.