20 degrees sounds excessive but don't know anything about SPFI engines etc.
On my 86 leone (EA82) it was 10 degrees btdc at idle (breakerless electronic distributor) with vacuum advance hose detatched using timing light ( with carburettor. for 91 fuel)
The vacuum advances/retards (plate inside distributor moves and centrifical weights advances rotor so advances timing up to 35 degrees ? (from memory) when rev engine with vacuum hose back on.
Can check this with timing light / timing marks?
Never had to touch/replace anything there in the 23 years l had it apart from checking timing (with light) twice.
Engine maybe one crank rotation out of phase for distributor?
Did you move anything? Did you put it back in the same way you took it out?
If moved engine can take no.1 spark plug out and check that no. 1 piston is at TDC corresponding with TDC timing mark, to have engine in phase. then distributor @ no. 1 etc etc.
Edited by subnz, 06 December 2013 - 07:08 AM.