I guess I should be able to study the IF from a simultaneous shock in Dynare correct ?
I am actually worried about whether this is usually done in the literature. Someone must have looked at say monetary easing shock following some negative TFP/risk/whatever shock (no ?). If you have such a reference I would be really grateful !

Hi, this is possible in Dynare by specifying a correlated shock. E.g. call the common epscommon and add it to both equations you want to perturb. Note that this is not usually done in the literature as most papers consider first-order approximated model. There everything is linear. Hence, there is not additional value of simultaneously shocking two variables as the IRF is simply the sum of the two individual IRFs.