I have the same problem. I've done both WBTB and tried WILDing during naps, with WBTB being the best results I've seen so far. I get the heart beat sensation too. I've only had one WILD in the past, and that wasn't even because I was trying. I woke up in the morning, fell back to sleep, and saw clear HI and a dream scene in front of me, as if I skipped all the hard parts of WILD. I also have concerns about actually getting past SP... I know how you feel about it disappointing, I think that too sometimes. I think we're both just focusing too much on what is happening, that's what probably is triggering the racing heart. We think we're about to enter the dream, so we get excited and our heart races. I think the way we would need to approach it would be to stay calm. I've been trying WILD for around 6 months, off and on, and I've been a lot calmer about getting through the different stages. It probably won't take you as long to get calmer, but just train yourself as if you are an experienced WILDer. For instance, if you get the tingle sensations, think nothing of them, focus on a dream scene you're trying to create. That's what I do at least, for the SP part, I get really aware because I know it's one of the last steps before entering a dream. Eliminate the excitement and anticipation and you'll be successful. I'll try this tonight too.