renault clio 1.2 2003-engine check light on

hi, posted the other day about my car losing power, its not getting up to speed as fast as it should it takes me ages to get to 20mph the guy at the garage thinks the 2 cylinders have low pressure. and said it could be the head gasket but i used real seal to fix the head gasket but still the same problem.

my car kept coming up with check engine light it flashed on and off for ages and now its just on constantly, any ideas what the problem is

renault clio 1.2 2003-engine check light on