Problems after spark plug change

I wonder if someone here can help, I did a spark plug, air filter and oil change and oil filter service over the weekend and now it is reluctant to start, runs rich (strong smell) and is a bit spluttery. This is a standard VFR, no power commander, standard exhaust etc. 

On further investigation (I apologise in an advance for my lack of technical knowledge but will describe things as best I can) the throttle bodies is it? - the four round things that open with you crank the throttle - as you sit on the bike I would number them 1 - left hand front of bike, 2 - right hand front of bike, 3 - left hand back of bike (nearest seat), 4 - right hand back of bike. Numbers 2 and 3 had smoke in them when the bike was off & numbers 1 & 4 were clear when and I cranked the throttle, this was after I had run it for a couple of minutes.

I did remove the whole airbox and had to replace it due to a stuck screw.  

There are no FI errors.

I realised I MUST have screwed something up but I don't know where to look! 

I would look at the following:

- plug gap size on all plugs

- that you have connected the correct wiring loom plug to each spark plug coil

- you have reconnected the MAF sensor, air temp sensor, bypass sensor (flapper valve controller) electrical plug connectors and all of the vacuum hoses that are under the air box

it has to be something simple for a regular service only

Put the old plugs back, see how it runs! New plugs are sometimes faulty.
An experienced mechanic said of fuel injection, "90% of the time checking electrical connections will solve a problem", so as Marooncobra said...check everything.

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