Golf 1993 cabriolet 1.8i Kjet running lumpy /misfire issue

Hi peeps
I need some advice please I've been driving my canny since March with no issues I left it on parents drive for 5 days.
Last weekend I picked it up to go for a drive out car started first time choke on everything fine choke went off and car started idling lower than normal drive her up the street  and she felt really lumpy and I notice popping sound from exhaust and what sounded like misfire.
So I've changed all plugs new leads and new dizzy cap and rotor had the car checked  this weekend  by a tuning guy who has set the timing checked CO he said everything is set correct and timing was out.
The car seemed to drive better but there is still a problem.
When on choke everything is fine when off.Car seems to hold back on acceleration and seems really bad at about 2-2,5 rpm almost feels like misfire  if you floor it car runs great and quite smooth I have run some expensive injector cleaner through it to see if it helps but doesn't seem any different  as anyone ever had this issue or can anyone help the guy who tunes car said it sound like injector I'm not sure everything was ok till I let it sit for a few days

Sounds as if you have a vacuum leak.
If the car runs fine choked, then a vacuum leak can cause this type of issue.

Check the brass screw on the Throttle body, if it can be turned by hand then that is a vacuum leak count the turns to remove it write that number down..  Take it and buy a new o-ring, return it to the count.

These critters don't like vacuum leaks at all.

Shell nitro mate for ages that's what was in the car when he tuned it and set timing
 checked for rust in fuel lines today all very clear changed fuel filter checked fuel pump only thing I haven't checked is injectors if I full throttle when driving it doesn't seem to do only at about 2 -2.5 rpm