hello everyone

apologies but i am fairly new to forums.

i have a 52plate st170

the issue i have is when starting the car, it can be abit hesitant starting but does start within a few seconds.

it then sounds like a misfire, splutter and as if it is struggling to run. the revs are at about 1300-1500 and after a few mins it then drops to normal idle speed and the engine sounds fine.

when driving sometime between 2000-3000rpm the engine can be hesitant again, splutter

i normally then drop a gear to be over 3000rpm and the thing just pulls like a train.

no problems with the car below or above when dirving but it is getting worse.

i have changed the following

spark plugs
leads
coil pack
air flow sensor
throttle body arribing this week.

could this problem be the inlet manifiold or the box of tricks that controls this?

if this is the case does anyone have a rough idea how much it would cost fit these?

really appreciate anyones help as i love my car and i know i spend a fortune on it but it is incredible to drive and puts a smile on my face.

happy to continue to spend the money as will never get tired of this beast.

thank you in advance