No offense but for RM400 budget changing to lightened crank pulley will help more for pickup... 

Good luck on your claim, previously also had some bad experience with Wai Heng, bad welding job, exhaust leaking after a month. The car also became noisy and no power after changing exhaust at Wai Heng. Beware that they will put your cataylst converter away, and hope you forget to claim it back. These 2nd hand catalyst converter can sell for RM80+. 

Warranty only void for the extractor lah.. Dont say u change extractor they go void the whole car warranty.
Btw for TS, some advise for u as we Personarians have been experiencing with so far (same case for saga FL cos the engine are technically the same)

1) modding the extractor ONLY voids the extractor part. Wont void the whole engine.
2) If want to claim warranty go to COSE. Damn easy to claim even if u mod ur car.. Install 17" rims also can claim for replacement discbrakes. XD
3) U want more low end torque go for Hotbits. U want high end power go for Powerzone. Hotbits the pipe diameter are smaller => faster gas flow => better low end torque. But top end power will be somewhat restricted compared to Powerzone. Powerzone extractor does not improve pick up much. Marginal increase, but top speed increases alot.. We are talking of reaching 220kmh here in Persona 1.6 IAFM with light mods.
4) IF and ONLY IF u have 4k lah.. Mb ur budget lesser, I can list the stuffs to upgrade in the following order.
1) Denso 0.4mm Spark plug
2) Works Engineering Drop-in Air filter
3) Grounding cable (VS barely gives u much improvements except smoother shifts at high speed)
4) Full exhaust set up. Extractor first if u dont have the budget. Then 2 swirl bullet or 1 swirl + 1 mid box followed by S-flow.
5) lightened crank pulley
6) lightened cam pulley

For engine maintenance
1) Caltex Havoline / Castrol Edge / Castrol Magnatec. Please dont use Shell Helix Ultra/HX7  .
2) AMSoil ATF
3) The correct brand of petrol. For best power Caltex > Esso > BHP > Petronas(this was tested with old Primax, the new Xtra fuel has not been tested yet). Shell cannot pakai at all. For best FC Petronas Xtra > Caltex > Esso > BHP.

These are all tried and tested by LYNPPC members as we all become white mouse and test different setup for best FC and performance. XD
LYNPPC - We kinda spam quite a lot there.