Bad cold start. Car re tuned and running poorly

So i was hoping someone would be able to help me, or give me ideas. I've been searching online for days and hours and can't find out what the problem is with my car.

It's an r33 with a RB25DET
Engine Mods:
Microtech ecu
Greddy BOV
Return flow fmic
Splitfire coilpacks
Pod filter

The car has been having bad cold starts seeing, it's starting to get colder. it would take* say, 4 or 5 key turns in the morning to start with the car sputtering, and trying to keep the revs up. Then while still cold (sometimes even when hot) the car would stall and struggle to keep the revs up. For example pulling up to traffic lights when going into first or neutral the revs would flat out drop. When stationary i find myself quite alot having to keep the revs up myself.

I decided it would be a good idea to get a mechanic to look at. The place i took it to, played with the microtech to fix the cold start idle rpm, fuel and so forth along with hot start. When i got it back the car was running great wasn't stalling on me, the idle was perfect.

Later that day i was having a look and having a play with my car, realised my BOV actually adjustable. So decided to take it off and have a look at it. Realised it was set all the way hard and the BOV wasn't actually going into the atmosphere because it wasn't making enough boost to open up the valve. I decided to adjust it to softer to see what it would sound like when it was actually working properly.

Upon taking it for a test drive to test out the valve i decided to give it a bit of a pounding. I managed to reach 180km and got complete speed cut (r33s come stock with a 180km speed cut) my car had never had speed cut before I've had it well and truly past 180km multiple times. So i was thinking it could of been something the mechanic did when he re tuned my idle?

Upon decelerating the car was running really choppy and wouldn't stop backfiring. Even when i slowed back down to 100 the car was still backfiring.

The car is now running really strange, it seems to have a slight miss when taking off in first gear. The car was vigorously shaking on idle the night i got the speed cut but has seemed to calm down quite a lot. but now it is decelerating and then accelerating on idle by it self. Sort of like a cammed car. It had a noticeable miss on idle. The car is putting out a lot of white smoke from the exhaust when changing gears after hit boost. I also changed the BOV back to where it was thinking it could be because the tune wasn't used to it, but it didn't make a differance.

Once i got home after the speed cut i looked in the engine bay and realised there was oil everywhere on the drivers side of the engine bay. I realised my oil dip stick had broken and wasn't sealing properly so i assume the oil came out of that as it seemed to have oil around it and at the very top of the dip stick. When i was adjusting the BOV i don't recall seeing the oil at that time.

I messaged the mechanic and let him know how it was and he said it sounds like a blowm off vac hose. I checked all the vac lines and they're all fine. Once i told him that they were all okay he started get defensive saying he touched nothing to do with the tune besides idle and cold start. And said he thinks it could be the turbo.

While checking the vac lines i realised there was actually oil leaking out of the BOV. And the BOV was making this awful wurring sound on idle.

So i wondering if anyone have any ideas?
When i get a chance next I'm goimg to take my turbo heat shield off and see how it looks.

I don't have enough money to take it back to them or another mechanic until payday. Which is a week and a half away. So my question is should i be driving it to and from work in the meantime or is it not worth the risk?

Any serious replys will be helpful!