Odd ball problem that solved itself today. It's a Volvo thing. But any ways my 87 B230FT started giving me problems in drivability. The stumbling, low power, Boost gauge was reading 10 inches of Vacumm instead of the 22 it normally runs at idle. When I would would give it some throttle I got a lot of Black smoke out the tail pipe and a lot of greef from the engine. Figured Oh great popped a hose in the Turbo piping. Pulled into a parking lot popped the hood and checked everything I could under the hood. Nothing loose, disconnected, no holes found, everything as it should be. As I pulled out I gave it some gas and I got a momentary hessitation. So being a typical guy I floored it, shifted into 2nd and ran her up to 5000 rpm at 12 psi of boost and you should of heard the knocking when the boost went up initially . There was a large black cloud behind me. Pulled up to the next light and she was running a lot better. When the light changed I jumped on it again, hit second (45-50 mph max)easing her up into boost and this time there were no clouds or knocking. There still is a little what I would call miss or slightly rough idle. I just ran a bottle of Tectron through her at the last fill up. It seemed to help a little. In April I put on new wires, plugs, cap, rotor, fuel filter, cleaned the K&N, throttle body and the entire turbo hose system including the Intercooler. It just started yesterday evening. Anyone have any ideas what's causing this. Bad Gas?, wrong heat range on Plugs? Plugs are factory OEM. The car does have 282,000 miles on it. The coolant level is fine so I have no loss due to head gasket problem. I figure it has to be something simple since an Italian Tune up cleared up most the problem.