I fitted a rs cosworth t3 hybrid on mine you need to knock the bulk head back to make clearance and a adapter flange welded to your manifold and a down pipe for it to fit as I specialize in them if you get stuck you can pm me I personally think it could be seals in the head or valve guides plus the 1.4 suffer from pistons craking around the ring area I am currently rebuilding a engine for a customer with all forge internals had the same symptoms as you for the same car