For semi-synthetic oils, the interval should be maximum 5000Km or 3 months; whichever comes first (as per user manual).
No adjustable tappets....For throttle body cleaning, just open the IAC valve and spray some WD-40. Set the ignition at 'ON' and then 'OFF' several time repeating WD-40 spray after each ON-OFF. Similarly spray WD-40 in the IAC housing in the Throttle body. Then spray some WD-40 at the butterfly. Just put back IAC and start engine. Give some throttle and again spray the WD-40 at the butterfly. It's Done!
Which gearbox do you have in your car. If it is 4-speed, 180+ km on motorway @100~110km/h is fine. As 100Km/h on a 4 speed gear box needs the engine to rev around 3200 RPM while a 5 speed gear box can attain a speed of 120km/h @3000 RPM.
Regarding the T:
It is located in between the throttle body and the CNG regulator.