not just a garage owner mate,he's a well respected tuner on this board and 99.9% of people would take his advice before yours im afraid,just need to look at his own car to see this
im sorry but your knowledge of rs turbo's isn't so good and you my friend are lookin like the newbie,i for one would not touch the boost level unless its gettin checked proper to see if theres enough fuel there,maybe 15 year back when they were new you could maybe get away with this but the earliest mfi systems are 15year old,like most parts this shows wear and tear and doesn't perform like it did back then,for £94 its well worth the money,if i had to say to you i could get another say 10-15bhp safely for £94 you would do it wouldn't you,anyway how do you know this guys cars not runnin like shit just now and another 5psi would end in melted pistons,you dont,thats why my advice is to get it seen to by a specialist not someone sittin behind a keyboard with a haynes manual

and my mate bought a rs turbo a couple of weeks back and was told this was A ok,we drove it home from liverpool with no hiccups and its was flyin,started first turn,no trouble at all,the guy said it had the boost turned down to 10 psi but was runnin 18psi,if we took his advice of turning it back up it would have melted as a rollin road proved the very next week,it was runnin very lean in 4th and 5th gear due to faulty fuel ecu,for £60 it saved him a 1k rebuild,well worth it imo