The temp sensor is not ported and plugs into the back of the airbox somewhere and does not plug up. The pressure sensors (one for each cylinder) hang on the back of the air box with vacuum taps coming from the throttle body throats. I suppose they could be plugged but more likely is an old and leaky vacuum hose.
Not a big fan of the K&N filter but I don't think that would cause the problem but it would not hurt to rule it out. Your symptoms are a bit vague so hard to say what it is. It could be worn throttle body shaft seals. One test is to start the motor and try to hold the RPMs steady at say 2000 and 3000. If it hunts then the throttle body seals might be leaking and leakage rate is probably random with throttle position.
