Mine was running about the same (on the lid thermometer) with two of three bottom vents wide open. The thermometers I had a grate level were reading a little higher. Particularly early in the smoke when the food is cold the lid thermometer tends to read lower than what you actually see at the grates.
If you want a higher temp, start with more lit coals. With more heat in the cooker, you get more chimney draft and the extra air continues the higher temps. You would also need to leave water out as it boils at 212°F and will tend to hold temperatures down.
IMO the temps you are seeing now are good unless you have a deadline to meet.