I have a 1997 900SE Turbo Convertible with Abbott Suspension mods, I was thinking of upgrading the ECU and maybe replace my 16" Viking wheels with 17" Viggen ones.
Has any one done this and if so what are your thoughts?

the 17'' wheels obviously give more grip (being wider and allowing for a wider tire fit), but be careful of tire choice as the extra width can introduce tramlining.

The reduced profile on the tyres will lead to more feel but with the side effect of perhaps more road imperfections transmitted through to the body of the car that the previous tyre/wheel combination soaked up.

As a result, being in a convertable (i.e. a vehicle structurally less stiff than a coupe) you may notice more scuttle shake on poorly surfaced roads.

Also, in reference to the ECU, the extra power surge could result in showing up the torque steer problems on the 900 more clearly. If going for a power hike I'd recommend that Abbott fit you out with their steering clamp and viggen rescue pack (bushes and or LSD)

Also, perhaps someone wants Viking wheels (if you're not keeping them for winter tyres) - it could reduce the costs of the changes, since the Vikings are quite popular. The Viggen wheels usually cost around £1500 with tyres - so shop around. Although elkparts do them :

SAAB 400129847 5-Spoke ALU34
7.5 x 17"

http://www.elkparts.co.uk/shop/index.html

Hope this helps

the 17'' wheels obviously give more grip (being wider and allowing for a wider tire fit), but be careful of tire choice as the extra width can introduce tramlining.

The reduced profile on the tyres will lead to more feel but with the side effect of perhaps more road imperfections transmitted through to the body of the car that the previous tyre/wheel combination soaked up.

As a result, being in a convertable (i.e. a vehicle structurally less stiff than a coupe) you may notice more scuttle shake on poorly surfaced roads.

Also, in reference to the ECU, the extra power surge could result in showing up the torque steer problems on the 900 more clearly. If going for a power hike I'd recommend that Abbott fit you out with their steering clamp and viggen rescue pack (bushes and or LSD)

Also, perhaps someone wants Viking wheels (if you're not keeping them for winter tyres) - it could reduce the costs of the changes, since the Vikings are quite popular. The Viggen wheels usually cost around £1500 with tyres - so shop around. Although elkparts do them :

SAAB 400129847 5-Spoke ALU34
7.5 x 17"

http://www.elkparts.co.uk/shop/index.html

Hope this helps