Wow, Maybe hearing mechanics dont deal with remove all spark plugs then compression test then put the all spark plugs back with hand tight then torque wrench to tight.
The compression test for bad gasket or piston ring or engine's cylinder cause loss power, I believe. I am saving the money to buy the compression test and backpressure. I already own the fuel pressure with fuel volume, engine vacuum, DMM, iPod touch (Scan tool for real-time with record, DTC, and freeze frame data) and test light for 12-25volts.