'TOP SPEED' is a little misleading. It's more a case of what is the maximum speed you can reach on the 1.6 mile runway before you have to drop the anchors, rather than what the car will do totally maxed out..
Last year I only did 1 top speed run in my Stage 2+ ED30, due to the fact it only had OEM cooler and I was more interested in the 30-130mph time. IIRC my official GPS speed was about 157mph, with the speedo reading over 170mph. If I had done a few more runs and braked later, I dare say I could of got a little closer to 160mph, but not much more unless I wanted to end up in the back garden of a Marham resident..
Good fun trying though..