I was assuming this. If you were doing the intercooler, battery and rad I cant imagine there will be any problems in that area. Have you checked the earths are all back on 100%? Does the car have an alarm fitted with an immobilizer? When you turn the key past ignition to engage the starter is there no noises at all? Does the dash flicker at all? Where were you having brackets welded and did you change anything in relation to the I/C piping that something could be shorting out on?