Hi Nazrat,
First, the disclaimer- try these suggestions at your own risk, I assume no responsibility whatsoever. (sorry, have to be careful these days.)

Next, the small bolt you mention is right underneath the heater hose,where the hose connects to the cyl. head. It requires a 1/4" wobbly 5mm allen socket. I got mine from the Snap-On tool truck, about $25.00. Or, a 1/4" stubby 5mm allen socket on a 1/4" universal joint. Then, with some patience,you can get the bolt out. But, I have never had success getting the tube out without removing the plastic intake plenum. This only takes an extra
15-20 mins. It requires a 6mm allen ball socket. If the ball breaks on the end of the socket, then take a 3/8" 12mm 12point socket on an extension and drive the socket on over the head of the plenum bolt and it will come right off.
If you do remove the plenum, be careful not to get anything into any of the intake ports. Also, there are 2 line-up dowels on the side of the cyl. head for the plenum. These can be knocked loose into one of the intake ports and get caught between the piston and cyl. head chamber roof. ( I forgot to mention there are 9 plenum- 6mm allen bolts.) HTH.
Paul