I've just bought a 1990 500SL, it's been a while since I've had a Merc (previously owned a 1990 230E and a 1998 E300TD) but was so disappointed by how awful the build quality was on the E300TD I never thought I'd buy another - but the 500SL was too much to resist!

I suppose I've had the car a couple of months and there are a few niggles I want to get sorted, I'm hoping someone on here might be able to help.

1) Rough running at idle. This only happens in neutral or park, the moment you put it in drive it's as smooth as silk. I can't see the 500SL at this age has a mass air-flow sensor but it does have this - VDO Idle Air Control Speed Actuator # 000 141 24 25 clearly visible. If this plays up can it cause these type of symptoms? Being a UK car it does not have a catalytic converter at this age so would it have an oxygen sensor if no cat is fitted?

2) Loss of power under hard acceleration. It's only done this once, it was like the fuel was being heavily restricted or cut off. I know it wasn't anything related to the ASR as I've had that cut it and know what it feels like, backing off the gas it ran fine, hard on it again it did the same, after about 3 times it stopped and has run fine since. I did see something about a faulty OVP relay somewhere, could this be on the way out?

3) It has ADS, I've not driven the car for nearly 3 weeks and when started the suspension was very low. It pumped itself up after a few seconds but the ADS light was on steady for about 5 or 6 miles until I stopped and put it in reverse. It went out, and has stayed out since. Is this anything to worry about, I have noticed the n/s/r corner feels a bit soft when driving over bumps compared to the rest of the car and wondered if the strut needs replacing or if there is some way to check or top the hyraulic fluid up in the suspension.

4) After leaving it for nearly 3 weeks the battery was stone dead. It has a Sigma S30 alarm/immobiliser fitted and I happened to notice a previous owner had fitted a dis-car-nect device on the battery terminal making me think it must have done this before hence the easy way to disconnect the battery. Is this a common thing with SLs or is it most likely the battery isn't too good?

5) Both the hard top and soft top don't seem to sit low enough on one corner at the back, like the mechanism doesn't pull them down far enough. When the soft top goes into place it seems to pull down further and then pops back up a little bit before the windows start to go up. Is this adjustable in some way?

Thanks in advance for any help!