bah blown

Hi
I have recently changed the timing belt and clutch on my Sierra. I also cleaned everything up including the injectors. I have not been on the road yet as it needs an MOT but turned it round in my drive, at first it was OK but then it sounded very lumpy and there was a strong smell of fuel. I took the leads off starting at the front, they all sparked well (white spark not sure if you should be blue, but ?) anyway got to number 4 and the plug cap had got lose so tightened it up and bingo it ticked over and revved up nice. During all this the smell of fuel was a puddle that was on the floor at the lowest point of the downpipe it was quite a puddle tbh. once the number 4 was sorted the leakage stopped. (it is a tiny gap in the silencer because you cannot feel any exhaust gasses coming out, but its enough for the fuel it seems) The car runs ok but it a bit fluffy at low revs as in I have to blip the throttle gently to keep it going when manoeuvring slowly.
I am wondering if its putting too much fuel in causing the fluffiness as it seemed a lot to lose while ticking over just because number 4 was not sparking, Or is it meant to be a blue spark and mine are a bit weak?
The car always struggled at the emission stage in the mot before.
I would be grateful for any pointers, I have the haynes manual for fuel injection but cannot find anything relevant
Thanks
Thanks

bah blown

Blimey, not even 1` reply, I know they are getting rare but ....