bogging between 2 1/2 and 3k rpm

[JDNISMO]

Ok guys, I drive a manual 95 240 with intake and a muffler shop 2.5" exhaust from the '2nd' cat back with a dtm style muffler. For the past couple of months my car has showed check engine light off and on, but always turns back off. For the past couple weeks the car has bugun to bog down from 2 1/2 to 3 thousand rpm. It seems like it should be an easy fix (maybe a sensor) but I don't know cause I'm kind of an idiot when it comes to engines(bear with me I'm learning). Anyways if anybody can pinpoint what that is then much appreciative, if not I was wondering if there are any techs in the lynnwood/everett/seattle area that would be willing to take a look at my car. thanks, josh