I don't believe the VVT has any effect upon output power. It's not like Honda's VTEC, which is variable lift as well.
1.8T VVT seems to be purely for emissions control. Look at the table of features for the various 1.8T engines - all the EU4 emissions compliant ones are VVT, whereas the non-VVT ones are only EU3...
Last week I was working at Nissan, and talking to one of their engineers about VVT on the Nissan engines (sad, innit? [

]). He said that the purpose of their VVT is to hold the inlet and exhaust valves open simultaneously, under certain conditions, to recycle exhaust fumes and hence lower the emissions.
I suspect the 1.8T is the same, because the VVT engines have no greater power/torque rating than the non-VVT ones.
Here's the table of 1.8T engine codes that appeared on the Briskoda forums (and probably elsewhere!) - check the correlation between VVT and EU4, it's almost 100%
AGU
Audi A3 1.8T, (all models?)
Skoda Octavia 1.8T FWD (Elegance, L&K), 10/96-8/00
Volkswagen Golf GTI, (dates?)
Output: 150 hp
Drive: FWD
Emission: Non-VVT, EU3
Throttle: cable
Injectors: small
Turbo: K03
Gearbox: EVS, EGY
APX
Audi TT, (dates?)
Output: 225 hp
Drive: Haldex 4WD
Emission: Non-VVT, EU3 (check)
Throttle: drive-by-wire
Injectors: big
Turbo: K04
Gearbox: ? (6-speed)
APY
Audi S3, (dates?)
Output: 210 hp
Drive: Haldex 4WD
Emission: Non-VVT, EU3 (check)
Throttle: drive-by-wire
Injectors: big
Turbo: K04
Gearbox: ? (6-speed)
AUM
Skoda Octavia 1.8T FWD (Elegance, L&K), 8/00-now
Volkswagen Bora 1.8T, (dates?)
Volkswagen Golf GTI, (dates?)
Output: 150 hp
Drive: FWD
Emission: VVT, EU4
Throttle: drive-by-wire
Injectors: big
Turbo: K03sport
Gearbox: EBN, ENJ, ESV, FDC
AUQ
Skoda Octavia RS, 8/00-now
Seat Leon 20VT Topsport
Output: 180 hp
Drive: FWD
Emission: VVT, EU4
Throttle: drive-by-wire
Injectors: big
Turbo: K03sport
Gearbox: EHA (Octavia RS, 5-speed, long gearing), ? (Leon Topsport, 6-speed)
ARX
Skoda Octavia 1.8T 4x4 Elegance, 8/00-now
Output: 150 hp
Drive: Haldex 4WD
Emission: VVT, EU3
Throttle: drive-by-wire
Injectors: big
Turbo: K03sport
Gearbox: FEX (5-speed, short gearing)
ARY
Audi A3 1.8T quattro Sport
Seat Leon 20VT Cupra 4
Output: 180 hp
Drive: Haldex 4WD
Emission: non-VVT, EU3
Throttle: drive-by-wire
Injectors: big
Turbo: K03sport
Gearbox: FHA, FEK (6-speed)
ARZ
Volkswagen Golf GTI, (dates?)
Output: 150 hp
Drive: FWD
Emission: non-VVT, EU3 (check)
Throttle: drive-by-wire (check)
Injectors: big (check)
Turbo: K03sport (check)
Gearbox: ? (5-speed)
AWT
Audi A4 1.8T (Quattro), (dates?)
Volkswagen Passat 1.8T, (dates?)
Output: 150 hp
Drive: FWD or Torsen 4WD
Emission: VVT, EU4 (check)
Throttle: drive-by-wire (check)
Injectors: small (check)
Turbo: K03 (check)
Gearbox: ? (5-speed)
AWU
Volkswagen New Beetle 1.8T
Output: 150 hp
Drive: FWD
Emission: VVT, EU4 (check)
Throttle: drive-by-wire (check)
Injectors: small (check)
Turbo: K03 (check)
Gearbox: ? (5-speed)
BAM
Audi S3, (dates?)
Audi TT, (dates?)
Output: 225 hp
Drive: Haldex 4WD
Emission: VVT (check), EU3
Throttle: drive-by-wire
Injectors: big
Turbo: K04
Gearbox: ? (6-speed)
BFB
Audi A4 1.8T (Quattro), ?03
Output: 163 hp
Drive: FWD or Torsen 4WD
Emission: VVT, EU4 (check)
Throttle: drive-by-wire (check)
Injectors: big (check)
Turbo: K03sport
Gearbox: ETT GDU (5-speed)