I do not know y you wants a 20i instead of 28i or 35i. But in my region, X1 only offers in 20i sDrive version.
I owned E36 318i, Integra B18c Type R and also a Prelude. X1 20i sDrive is a down tuned engine but the 8 speed amazed me on test drive and strongly believe a tunes will bring this beauty to a beast. Therefore, after 3,000km engine life, i bought a tunes to satisfy my thirst in throttle response and engine responsiveness. I am 65% satisfy with my ride in Hong Kong but i bet this figures drops when considering driving aboard. I bet 28i sDrive is what you'll need as it could be as fast as a 35i stock after a piggy back tunes. However, 20i cannot as it is running higher compression ratio with original config.