ok its 97 sc300. 141100K. runs fine without check engine light on. Was misfiring-fixed that with the help of a tune up. Now after a tune up it reaches 4000rpm and after that it looses a tonn of power and torque. not as quick as it was before-it literally drags its nuts on the ground after 4000 rpm. changed all the spark plug wires and spark plugs-twice, new fuel pump and filter. distributor cap. Still the same ****. Than i took it to a mechanic and he said he really could not find anything mechanically wrong. He hooked up OBD-reader and Diagnostic-reader and said that that everything reads up to 65% than it cuts of electrical currant in the wires and does not show whats wrong. I found all the ground points, cleaned them, changed battery. Last thing on my mind check alternator, compression and torque converter, but i just cant think of anything else.. So if you have an idea whats might cause PLEASE LET ME KNOW.