Nooooooooooo!!!! Don't give it everything you've got! Your next 2 weeks will not affect your overall fitness, you should be tapering for sure not going strong. You need your body to relax from all that hard training you (hopefully!) did
You should be reducing the distance of your sessions from 3 weeks out... but you should still keep the intensity where it was. This keeps your body in the racing frame of mind.. but allows it to relax. It's normal for people put on a little weight and start to feel a bit lethargic during taper... but don't worry, you need to arrive at the start line rested rather than happy you just nailed a 10 x 1km rep tempo session 2 days before!
Do a few brick sessions.. reduce your overall sessions per week.. and start visualising yourself crossing that line in under 14 hours
The race only really starts on the marathon ... so lots of positive thought about dealing with heavy legs, and about getting your nutrition in ON THE BIKE (where its easier to digest / absorb)
90% of it is in the mind ... so get to the start happy and rested.. and you will be IRONMAN!!!!!!
p.s. which are you doing? really, really REALLY good luck!