Have you tried checking the wires coming from your injectors?? Glad it's sorted, I seem to have a similar problem on mine so first thing I do tomorrow will be check all mine!
You just leave the standard recirculating dump valve on the efi pipe, that will cover the hole. Just take the Vac line off which goes to the manifold to stop it opening
x2 What Phil said. I had gravel for 6 months with the Corys and they were absolutely fine. I kept an eye on there barbs and they never got damaged and they seemed perfectly happy. Then I changed to sand and they've always got there head in it I think they prefer sand but should be fine on gravel if it's small and fairly smooth
^ lol Steve when you get your fish I highly recommend Corydoras or "Corys" There really docile, keep your tank clean as there bottom feeders and really interesting to watch!
Here's a few of mine, not the best pictures but you get the impression Kribensis Cichlid Any my Orange Lazer Corydoras 2 short videos of when I first had the tank about a year ago on my Youtube page: http://www.youtube.com/my_videos?feature=mhee
I agree with getting a mild steel one, all the ss ones tend to crack. Stainless looks nice but is brittle, doesn't like going from hot to cold all the time! Had to have mine welded after less than 1000 miles Good choice on the Wepr mate