Exhaust Manifold to Silencer Sealing

The std TVR method of sealing at this point is a cup at each pipe end and a metal olive which with plenty of exhaust 'ponge' will seal for a limited time, until engine vibration and speed bumps crack the joint.

My simple fix for this is to weld the olive in the middle a short length of pipe which is the the right outside diameter to fit snugly inside the manifold and silencer pipes and the olive on the outside of the pipe gives you something to tighten the two pipes up on. So far this has been working / sealing with no ponge required for the last 4 years.

Thanks to Matt Feasey

De-misting

My 350i was generally pretty 'disappointing / challenging' when it came to seeing out in wet weather, I found a few things which have helped the windscreen demist;

Duct Tape
The ventilation system on the wedges is made up of bent and folded plastic and on mine a couple of seams were leaking  also around where the 2 dashboard vents are these just poke thru some ancient foam rubber. Which then leaks air so nicely heating the back of the dashboard. In both these cases plenty of duct tape over the joints and seams suddenly found a lot more air making its way to the windscreen vents.
 
Screen Vents
The standard screen vents don't do much in the way of directing air to where its needed although they are better than nothing, I've found a good replacement is those from a  Mk2 Ford Fiesta as the vanes on these are exposed and so stick into the duct and act as turning vanes to direct more air at the screen. They do need a bit of trimming to fit the holes but breakers yards don't exactly charge a lot for them so get a  few spares and experiment.
 
Vent sizing
The std vents are all opened by the same amount and you'll find that most of the air charges out of the centre vent and in front of the driver gets a sad little whiff.  The vents are easily removed with a lever of some sort and then  just tape over the bottom of the vents to block the holes off, obviously leave the drivers side alone but reducing the centre vent holes and blocking off some of the passengers helps get the air to where it should be.
 
Heater Box vane
The standard fan is mounted on the side of a folded plastic box which is then pressurised by the fan, the dashboard  vents are fed directly from this box and so get the best airflow (helpfully), whereas the ducted air (footwell and screen) is taken from the bottom of the box below the fan outlet. To force more air into the ducted portion of the system I removed the fan and then fitted a turning vane / blanking plate to force most of the air from the fan into and through the heater matrix and ducts.

Thanks to Matt

Water ingress
 
Although the wedge isn't the most watertight of convertibles you can make the best of its sealing if you rub all the seals with Vaseline as this softens the rubbers and helps it seal, also you can adjust the angle of the door glass runner  via 2 small bolts on the underside of the door towards the front.

Angling the glass so that the top points towards the interior will force the glass into the seal  harder, although you may have to open the door to wind the window up if your window motor isn't too hot!

Also the perimeter / door seal from an MGF will fit with a bit of cutting about and features moulded corners, gutters etc and generally does a better job of sealing.

Thanks to Matt

Engine Pinking

If you have pinking problems, and this is common with the low octane petrol available these days, try diconecting the vacuum advance mechanism. Simply remove the tube but make sure that you "cap" the pipe on the throttle body.

This will prevent the engine advancing too much at low revs, and you can possibly even advance timing, but as a guide 28 degrees @ 4000 is good. If you can get 30 thats fine but unlikely on the hotter engines such as 390/ 420/ 450's.

Thanks to Tim Lamont of Act Performance Products.

Ignition Module

If you need to replace the ignition module, make sure that you fit a Lucas part. Cheaper ones don't last anywhere near as long.

Thanks to Tim Lamont of Act Performance Products.

Spark Plugs

When replacing the spark plugs NGK are about the best BP6ES or B7ECS (competition).

Thanks to Tim Lamont of Act Performance Products.

Engine Oil

The Rover engine has a high capacity / flow, but low pressure system, therefore a low viscosity oil is not really ideal. Most basic mineral oils are OK but tend towards the heavier viscosity. Change every 3000 miles.

Thanks to Tim Lamont of Act Performance Products.

Rev Limiters

On pre-hotwire cars it is a good idea to fit a Rev Limiter, especially If you do trackdays or are a complete maniac. These cost in the region of about £50 - 60 but could save your engine if you miss a gear at a critical moment.

Thanks to Tim Lamont of Act Performance Products.