how you doing stu been a bit busy so missed your message, i think your car needs to start with basics, ie oil pressure test for start, i had one that i bought after it done its turbo and it went in to diesel runaway ie all its engine oil got just as fuel and it seemed after that all was well but kept not boosting right and it really got me spinning trying to find the issue, the issue was main end bearing worn out from the over run and lack of oil pressure to float the turbo bearing and this caused drag on it so would not make the boost until engine rev's higher ie more revs slightly more oil pressure then would boost,, mine in the end was killing turbo's 1500 miles.. so hot engine oil pressure test think you need first off. filing that and you want someone to look at it i do a few timing chain jobs for a tuning company he's proper good fair on price and acn remap and dpf deletes etc, he can also read your ecu and sensors on a deeper level than i can or autocom can,, but like said need to know you have the basics