there is restrictions in clyinder 2 and 3, the 3rd being more restrictive, if you dont take them out then you will get a build up of pressure on the cylinder rings and they will wear out along with cracking the manifold, if you port it then both the above should be heavily reduced removing both and giving the others a good porting then it will be fine to run as much boost out of that ct9 as you want, in most cases the ported mani will spool up quicker because of the shorter runners the jam ct9 manifold was a replica of the oem one just ported, it also blocked out passage between 1/4 and 2/3 to stop any pressure going back into the other runners