Vyvanse and Wellbutrin

I've been taking 300 mg of Wellbutrin for over a year now. I started taking Vyvanse 40 mg 6 weeks ago. I noticed that the Vyvanse started to feel much weaker as the weeks went on, so I decided to take a 5-day drug holiday. Since restarting I've had a lot of trouble sleeping and my heart rate's been through the roof. This wasn't an issue before, or at least I don't remember it being an issue when I initially started at 40 mg.

I've tried doing a lot of research and it seems like the interaction between Wellbutrin and Vyvanse can either be synergistic or problematic depending on the person.

If you currently take Vyvanse with Wellbutrin what has the experience been like for you? What doses do you take?