Robot Turning Using PID

Question

I currently have a PID algorithm to control my robots turns in an autonomous state. My robot has encoders, on each motor, which there are four of, and also a BNO055IMU. Furthermore each motor is a never rest 40 motor from Andymark, and unfortunately I am stuck with encoders that do 3 pulses. I would like to improve the accuracy of my turns either by using a different algorithm or improving my current one.

My Current Turning Code:

 public void turn(int angle, Direction DIRECTION, double timeOut, int sleepTime, double kp, double ki, double kd) {
    double targetAngle = imu.adjustAngle(imu.getHeading() + (DIRECTION.value * angle));
    double acceptableError = 0.5;
    double currentError = 1;
    double prevError = 0;
    double integral = 0;
    double newPower;
    double previousTime = 0;
    timeoutClock.reset();
    while (opModeIsActive() && (imu.adjustAngle(Math.abs(currentError)) > acceptableError)
            && !timeoutClock.elapsedTime(timeOut, MasqClock.Resolution.SECONDS)) {
        double tChange = System.nanoTime() - previousTime;
        previousTime = System.nanoTime();
        tChange = tChange / 1e9;
        double imuVAL = imu.getHeading();
        currentError = imu.adjustAngle(targetAngle - imuVAL);
        integral += currentError * ID;
        double errorkp = currentError * kp;
        double integralki = integral * ki * tChange;
        double dervitive = (currentError - prevError) / tChange;
        double dervitivekd = dervitive * kd;
        newPower = (errorkp + integralki + dervitivekd);
        newPower *= color;
        if (Math.abs(newPower) > 1.0) {newPower /= newPower;}
        driveTrain.setPower(newPower, -newPower);
        prevError = currentError;
        DashBoard.getDash().create("TargetAngle", targetAngle);
        DashBoard.getDash().create("Heading", imuVAL);
        DashBoard.getDash().create("AngleLeftToCover", currentError);
        DashBoard.getDash().update();
    }
    driveTrain.setPower(0,0);
    sleep(sleepTime);
}

NOTES: when driveTrain.setPower(x,y); is called the left parameter is the power set to the left side and the right parameter sets the right side.

Direction is an enum that stores wither -1, or 1 to switch between left and right turns.

Dashboard.getDash.create is solely to keep a log on what is going on.

imu.adjustAngle does the following:

    public double adjustAngle(double angle) {
    while (angle > 180)  angle -= 360;
    while (angle <= -180) angle += 360;
    return angle;
}

imu.getHeading() is self explanatory it gets the yaw of the robot.

My current values for pid constants. (They work pretty well.)

KP_TURN = 0.005, KI_TURN = 0.0002, KD_TURN = 0, ID = 1;