[Engine] Turbo help

[unibiggle]

Hi everyone

I have a citroen berlingo hdi 1.6, recently had the engine reconditioned and a new turbo fitted from a local garage. was working fine until the turbo started cutting in and out.

I took it back and they tried several things but to no avail, still no turbo.

they put a cheap euro spares turbo on and have replaced the pressure solenoid but still no joy. They wanted to charge me £440 for this but i didn't pay and I'm now stuck with this problem.

Can anyone point me in the direction I can try to fix on my own? at the moment the turbo kicks in for about 5 seconds every 5 minutes. There is also smoke coming out the exhaust

Many thanks hope you can help