im currently looking at a few Volvo 1.9 turbo diesels and need advice on the engines, as there a renault unit. im new to diesels so wouldnt now a good one from a bad. one i looked at recently would run ok but when reved while standing a plum of white smoke would appear, this made me walk away without even test driving it, as i thought if it makes this much smoke at normal intake pressures whats it gonna be like when the turbo kicks in. anyway i may be not reading the signs right so need some tips on how to test one before purchase.