Hello, we've replaced the timing chain kit on a 58 reg Golf 1.4 TSI which had been diagnosed by another garage who had recently serviced it.
The timing was out so we replaced the kit and rebuilt it with a new water pump(magnetic clutch type) which had a small leak.
The compressions seem ok, ranging from 150 to 135 but there is a slight misfire noticed at idle and around 2,000 RPM. There initially wasn't any fault codes but after around 2 weeks, fault code P2015 logged but didn't bring on the engine management light.
We accidentally noticed it seemed better without the engine cover vacuum reservoir connected. Could the fault code be generated from not having the vacuum pipe connected?
We've rechecked the timing and reinserted the tools and it seems fine. TDC is checked with a gauge and could possibly be very very slightly off?? The owner says it ran fine before?
Any one come across anything similar before?

John