Evil horse said it perfectly, just because his old owners did ground with him desn't mean the lessons will travel over to you, sure he knows to move his ass when you flick a rope at it, but the respect? No.
And don't say you've taken the right amount of time because you didn't immediately jump in the saddle, taking the right amount of time when the horse is ready. Yes you have to push them, but not drag them.
Excuse my bluntness but I'm also worried about your experience. The fact that you said the horse you've trained before was the best you own, compared to a really nice horse, well, doen tell anybody much. Have you ever rode a Professionarily trained horse? It's like a punch in the gut at first when you think back to all of your hard work on your own horses, but it makes you better. Strive for lightness and suppleness with your colt, and really instill the basics before jumping forward.
Also, realize it takes a whole lot of time to train a speed/barrel horse. Patterning him will take you at the very least 6 months and than MAYBE you can go faster than a slow lope. And that's after you have him nice and broke.