Lude Generation

i have a 4th gen with the f20a4 engine and it has this splutter / hesitation when you apply a little throttle from idle , so you are in traffic and you need to just move forward a little bit , on idle no problem then you give a little tickle on the throttle thats when it kinda does nothing for a split second then it coughs and splutters you get a tad of whiplash then your off , its only this first bit of throttle any other part its fine , car has only been up and on the road a few weeks now after being in pieces for 8 years so any previous engine problems are unknown , before the engine was fitted i did carryout a full service on it which was replacement of both cam belts and associated components , new water pump , new plugs , dist cap rotor arm , check and adjust valve clearances , new thermostat , oil +filter , fuel filter , i am wondering maybe a vac line could be mixed up on reassembly

Possibly a mixed up vacuum line as you say, or split/leak in the intake pipework, or idle not adjusted quite right/iacv/fitv not set up right, or sticking, or leaking gasket/seal on them. Those are what I would suggest starting with...

TPS worth looking at too, caused me issues like this

vacuum leak could be likely cause,

check dizzy cap condition, could cause poor running

Could be the timing too maybe?

i now have a complete original air filter assembly so will be fitting that and bining my boy racer cone filter and checking all the vac lines , dist cap and rotor are new will slowly go threw all the other items mentioned make sure they are all ok one by one give me something to do over christmas break