Congrats with the new car. The B21FT is a low compression K-jet engine with a big T3-turbo. Turbo lag is an understatement!!!
The stock engine puts out a whopping 135 bhp (around 105 whp) in stock trim, about as much as a high compression 2.3L engine without turbo lag. But the engine is nearly bullit-proof and can take lots of abuse. In the old days it was the engine of choice for tuning projects.
All the lost knowledge and black arts of tuning B21FT K-jet engines is hidden in the 'Articles' section. The button between 'HOME' and 'Community'.
First do a stage 0: Change all filters, oil, plugs, plug wires, rotor and cap. Clean the flame trap and replace all the old vacuum hoses with blue silicon (get rid of all the vacuum leaks and looks much better).
To get more out of the engine and to reduce lag, you need to improve breathing (in and out), raise the boost and cool down the intake air.
The standard modification list looks like this:
Modify the airbox (See Articles section)
90+ exhaust manifold + T3 turbo or at least 15G.
NPR Intercooler + silicon intercooler hoses
MBC + more boost
3" downpipe + sport exhaust (or just remove the middle muffler)
Cam upgrade (A, B or IPD turbo cam)
OBX header
B21F (Swan neck) intake if you want to keep K-jet.
Doing all of the above will get you close to 200 bhp, maybe more.
Above this the K-jet system becomes a limiting factor.
You can do the 'terminal 11' mod (See 'Articles')...but that's about it (unless you have $$$$ to burn).
NEXT:
B230FT intake + Microsquirt
Accumulator Mod for AW71
IPD turbo, V, K or H-cam.
T3/T4 .50 trim, HY35, HE341CW or HE351CW
Raise boost to 2 bar