Problem after replacing 1999 2L Mondeo head gasket?

I recently attempted to replace the head gasket on my 1999 2.0L mondeo after I found water in the oil and a lot of white smoke in the exhaust after an "overheating incident".

The engine will now start, and runs (albeit lumpily - but I have only run it stationary, not actually driven it anywhere so kinda expect that) but there is now a continuous kind of blowing noise, not like a pulsing sound like I would expect (just guessing here) if it was a cylinder leaking somehow - but a steady constant blowing. Theres no sign of leaking oil or water anywhere tho.

I am worried that I might have damaged the gasket on installing as my torque wrench seems to have trouble with low numbers, and it didnt click on the 11ftlb the manual (haynes) recommended for initial tightening, and I ended up going a lot tighter on a few of the bolts before undoing them and starting again... and Im not sure I should trust what its telling me on the 30ftlb either...
Or could it possibly be that its not tight enough?

Any suggestions/advice gratefully recieved :)