Remove, clean and refit EGR (exhaust gas recycle valve) Guarenteed it will be clogged up. Quite an easy job if you can gain access on Laguna. 3x10mm bolts, elec plug and slides out. Clean/scrape coke and make sure valve moves.
It happened on my 2001 Espace 2.2Dci. Once I cleaned it, got improved power and fuel consumption.
Hope this helps.
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