Volvo Repair: engine lean condition....exhaust red, lean condition, hall effect sensor

Question
I have a 89 740 turbo that stopped while driving one day. Upon inspection I discovered the ignition module faulty. After I repleced it I found the Hall Effect sensor bad so I replaced the entire distributor. On test drive the engine ran fine for 5 min but as it heated up it began to loose power and the exhaust was red and glowing. Thinking I had a clogged exhaust I removed the cat and mufflers but no change. I am out of ideas and desparate for any clues.

Answer
Hello Paul,  The one thing that stares out at me is a possible fuel injector not opening long enough.Accompanied by a slight engine miss.Also spray glass cleaner on the ignition wires,it adhears to the wire surface better than plain water.Intermitten 'hot spark' from a poor contact in the wires can create an 'arch' and make the spark plug tip very strong,ie., 'Hot'.That combined with low output from any injector, can make for a very lean condition. Don't overlook the turbo itself,take the hose to it off and make sure it spins free,no side to side,up or down or in and out motion,if there is then when it heats up it locks up and blocks the flow.Thank you and good hunting!   PKD