Cranks but won't start

[Tamkat]

Hi guys. I may just be repeating what others have already posted but here goes.
Just completed plugs and Coil overs change. New oil and filters etc. Car will not start. Cranks but no fire. Have checked and rechecked everything is back on. Not sure if computer issue or not. Will crank over for 5-6 seconds. Getting backfire through exhaust and air filter.
Any suggestions would be appreciated.

 

[Ozzie]

Are the hoses all where they should be?
Shouldn't backfire at all being alloytec

 

[greenacc]

Did you lift the upper intake right off? Might have squashed a hose when you put it back on.
Was everything working before you did the service?