My 92 Spirit (2.5) has developed a misfire which occurs only when the engine is really warmed up. Especially after freeway run. I really feel the miss at idle. It is hard to detect at high sppeeds other than the engine being a "little" sluggish. Things go back to normal after cool down. I have done a tune up consisting of plugs, wires, dist.cap and rotor which were needed but did not help. I am about to use a heat gun on the coil then the distributor to heat up the pick up coil. I cannot find what the resistance values should be for these. I would appreciate any suggestions.BTW- I only have the usual code 55.