FYI, you dont need backpressure in your turbo car. The more open up your exhaust the better for power, so dont worry about the exhaust leak as it relates to your issues.





Your first issue sounds like a carbuerated car with an improperly jetted accelerator pump. Based on that I would probably first look at air/fuel related things like maybe plugged fuel filter, etc



The second issue, intermittent problems often are electrical in nature. Whether its a short, open, faulty module etc. The car bounces around and the problem can come and go. With the electrical load being related I might take a look at the battery and alternator connections. Possibly one or the other of them is not continuously providing the power it should.