We pulled the injectors on our Volvo 2003T at about 1000 hours a few years ago, and found one WAY off spec, and the other 2 marginal. Engine had been running OK

We replaced all 3 with factory rebuilt (from a UK Volvo shop at half the price US Volvo charges)

Also cleaned out the exhaust elbow at same time. It had under 1/8" build-up

Now we are at 2000 hours. Engine runs OK, but seems to perhaps have less pep that at 1500 hrs. Starts easily with a blast of black smoke, then runs clean

It has been used about 2/3 for motoring at about 60% load, and 1/3 of the time for batterycharging/freezer, which is about 7% load.

Shouls we re-do the injectors?

Should we be dismantling the exhaust elbow and cleaning it?